Personal Combat Sims (Almost always shortened to PCS by the game) are a new mechanic in XCOM 2, though they could very loosely be compared to Gene Mods in Enemy Within and so argued as not completely new. They're one of two kinds of battlefield loot that can be turned around and applied to your soldiers, with the other being Weapon Attachments, which will be covered next post.

 In the case of PCSes, each soldier has a single slot for a PCS. By default, once you've installed a PCS you're not getting it back; installing a new one will destroy the old one. In base XCOM 2, there's a continent bonus that means the old PCS will instead be returned to your stores, and in War of the Chosen it instead shows up as a Breakthrough, but neither of these is guaranteed to show up in any particular run so you can't count on it.

 Returning to the 'battlefield loot' notion; sometimes when you kill an enemy, it will drop loot that, if you actually want it, must be picked up by one of your soldiers (Or the mission end in your success) before it times out and is destroyed for... some reason. This will always require moving a soldier to a clearly marked 3x3 grid centered where the unit died, and you always get exactly three turns before it times out. Note that the soldier who picks it up is, in fact, carrying it; if that soldier dies? They'll drop it, though now with an inexplicably generous four turn timer, and you'll need somebody else to pick it up. If they get left behind one way or another without outright dying? You won't actually get the loot, because it stays behind with them.

 Also note that if the enemy who was carrying the loot is killed with explosives, their loot will be explicitly announced as being destroyed. As such, while you're not consistently punished for murdering everything with explosives like you were in the previous game, it's generally better to avoid outright finishing off enemies with explosives just in case. It's... worth mentioning that the game assigns loot when generating enemies. First, this means it's gameable with save/load shenanigans if you want to abuse explosives without consequences; simply save at the start of each turn, and if the game informs you that you blew up loot? Reload and just don't kill the relevant enemy with explosives. Second, there's actually at least one mod that will outright mark which enemies are carrying loot for you.

 To be honest, I feel like this aspect of said mod really ought to have been the base-game behavior if they were going to go with this approach to timed loot. Like okay yes it doesn't make 'realistic' sense for your troops to always magically know which soldier is carrying loot, but the fact that only specific designated enemies drop timed loot doesn't make much realistic sense in the first place; it'd be one thing if, for example, a Conditioning PCS would be dropped by a Trooper who actually had appropriately boosted HP, but as-is the system is pretty obviously a game-y system that only very abstractly represents opportunistic looting. Really, while I like the timed loot system in a general sense, the details of how it was handled are pretty confusing. I'm moderately sympathetic to these issues due to this being a new mechanic outright, with no precise antecedent in a prior XCOM game, but only moderately because the actual chain of decisions regarding timed loot really just plain confuses me. There's nowhere I go 'okay, that's not how I would've handled this, but I can understand what the thought process was and it's not a bad one'. I have difficulty pointing to any single failure point because fundamentally I can't imagine arriving at something like this system; if I went with opportunistic battlefield looting, I'd do something like root it in the player having to cart off ADVENT soldier bodies (So that battlefield looting would be designed around having to impair your squad's fighting ability in the short term, sacrificing immediate advantage for long-term gains), or make it so every dead enemy dropped some timed loot (And just gloss over the timer issue as a pure gameplay mechanics thing) with most of the loot being stuff like a little bit of Alien Alloys, the loot of the actual game interspersed at around the rate it is in the actual game and just rare by comparison to the less valuable loot.

Anyway, bemusingly, just like in the previous game killing an enemy with explosives will vaporize their stuff but once it's been dropped it's completely explosion-proof. So don't worry about catching loot lying on the ground with explosives. Nor is anything else capable of destroying it. (I'm not sure what happens if your soldier carrying loot is killed with explosives; it's not something that crops up readily in normal play) Once it's on the floor, timing out is the only way for it to be lost.

 Loot itself can be made of multiple different objects, and are any of PCSes, Weapon Attachments, Elerium Cores, ADVENT Datapads, Alien Data Caches, and in War of the Chosen 'Chosen Information'. Datapads/Data Caches can be studied repeatedly as Research topics, trading research time for Intel; Alien Data Caches are worth more than ADVENT Datapads, but also take slightly longer. Note that each time you convert one to Intel, doing so again will take longer, stacking infinitely -also note this is per type. Cracking an ADVENT Datapad makes cracking ADVENT Datapads take longer, but Alien Data Caches are not affected by that, cracking Alien Data Caches makes future Alien Data Caches take longer to crack but doesn't affect ADVENT Datapads. Elerium Cores are spent on the vast majority of Proving Grounds Projects. Chosen Information halves the time the current Covert Operation for a given Chosen's personal mission chain will take -if acquired as random loot on the battlefield, you won't know which Chosen it's going to affect when you loot it, and in fact will have to manually check through the Resistance Ring to figure it out. If you buy it through the Black Market instead, you will know exactly which Chosen you're choosing to speed toward.

 On the topic of the Black Market, it almost always has at least one PCS and at least one Weapon Attachment for sale each month. This pretty consistently starts out with Basics on offer, then drops them in favor of Advanced, then drops those in favor of Superior. The price does scale up, but not as fast as the quality; I personally don't bother to buy anything below Superior, unless maybe a particular run is being really lucky with Intel amount. And even then I'd generally rather spend Intel on an early Engineer or something like that, if I have Intel to burn early in the game.

 Each PCS is a boost to a single stat on the soldier, and comes in three possible tiers; Basic, Advanced, and Superior. Toward the beginning of the game, you'll tend to find Basic versions, with the occasional Advanced and rarely Superior versions, but as you progress through the game the average quality of what you find will rise until eventually it's surprising if a drop isn't Superior. For some PCSes, the exact numbers provided are completely predictable based on the tier, while for others the quality has its boosts occur in a random range; in two of the latter cases, this means a given Advanced isn't necessarily better than a given Basic, nor a given Superior necessarily better than a given Advanced.

 In this post, I list one number/number range in parentheses. In the base game, the parentheses values are what the PCSes are set to once you've purchased the Integrated Warfare project from the Guerrilla Warfare School. In War of the Chosen, that purchase no longer exists; instead you can get the same effect as a continent bonus or from a Resistance Order. (Still named Integrated Warfare either way, note) This means PCSes are a bit less appealing in War of the Chosen, on average; you can't assume you'll get them boosted like you can in the base game, and even if your run has access to the boost that doesn't necessarily mean you're making use of it. After all, continent bonuses get increasingly expensive to unlock (Due to rising Radio Relay costs), while Resistance Orders all compete with each other, such that you might not be able to justify the slot on something so limited.

 Note that in War of the Chosen PCSes are less commonly looted. Lost will never drop timed loot and displace ADVENT/Alien troops when they show up, Vulture is no longer guaranteed to acquire, and the Chosen tend to reduce how much timed loot you find if you're staying on top of them, due to them displacing a pod that would otherwise have spawned and so occasionally removing a pod that would've dropped loot. It's also possible War of the Chosen has outright adjusted the loot tables, though I'd be a bit surprised if this is a contributing factor.

 Also note that PCSes can't be equipped until you've built the Guerrilla Tactics School. I'm not entirely sure why, to be honest; this has no obvious narrative/thematic basis to explain it, and gameplay-wise the GTS should always be one of your first Facilities. Even in War of the Chosen where you normally should build the Resistance Ring first, it's not unusual for a run to have built the GTS before you've even found a PCS. So... why does this requirement exist? It basically doesn't matter. Even more confusing is that Rookies are always forbidden from equipping a PCS; I'd get it if, for example, Psi Operatives were forbidden from equipping PCSes, but as-is I have no clue what could be motivating this decision.

 Anyway, let's get into the individual PCSes.

Focus
Adds Will to the soldier.
Basic: 10-15 (13-20)
Advanced: 15-20 (20-27)
Superior: 20-25 (27-33)

Focus is the only PCS whose value radically shifts in War of the Chosen.

 In the base game, Focus is a bit of a trap choice. As soldiers gain levels, their Will rises; this effect caps out at 100 Will. Their Will is allowed to go over 100, but not through leveling... and the game counts PCS-derived Will against your soldiers for this purpose. In other words, if you slap a Superior Focus PCS onto a soldier early in their leveling, you're permanently crippling their maximum Will.

 Once they're at Colonel level, feel free to slap a Focus PCS on them, but not before. Also keep in mind that in XCOM 2 Will does not help for psionic offense, so you shouldn't be trying to save Focus PCSes for your Psi Operatives.

 In any event, in the base game Focus PCSes are basically a way to better prep soldiers for psychic threats, and that's about it. Once you've got Don't Die On Me, any soldier who reaches 100 Will is guaranteed to go into Bleeding Out mode when they should've died, making further Will boosting irrelevant to that purpose, and in the base game Panic is fairly rare and not something that provides a clear guidepost on who you want Will-boosted. You could prioritize Revival Protocol Specialists on the idea that they'll clear Panic on other soldiers, I suppose, but clearing Panic with Revival Protocol is generally a dubious thing to be doing: a Panicked soldier doesn't, in the base game, get to act on the turn you cleared their Panic, after all, and it's very rare for a soldier's Panic to last the additional turn it would take for Revival Protocol to have done anything of use. Furthermore, unlike the prior game, there's not really a matchup consideration: if you don't have the Alien Hunters DLC, no enemy specifically attempts to induce Panic, even into War of the Chosen. If you do have the Alien Hunters DLC... I suppose you could put a Focus PCS on whoever you intend to carry the Bolt Caster shortly before you expect to fight the Berserker Queen? That's not exactly a clear, strong niche for Focus PCSes, though.

 In War of the Chosen, Focus PCSes are suddenly actually pretty good! There's the obvious point that you don't have to worry about soldiers missing out on maximum Will from installing a Focus PCS too early (Covert Operation slots that permanently increase Will don't enforce the old cap, for one), and there's the other obvious point that Will is now central to the Fatigue system. It won't necessarily affect longer or more enemy-dense missions since the main sources of Will drain have a percentage-based mission cap anyway, but a Focus PCS can help keep a favorite soldier able to be tapped for several short-ish missions back-to-back without ending up Tired. Conveniently, it increases not only maximum Will but also current Will, so you can apply it literally just before sending a soldier in if for some reason you'd like to maximize the odds of a particular solder being rested right after the mission -maybe you have a Covert Op you need them for in a couple days, for example.

 Note that slapping a Focus PCS onto a Tired or Shaken soldier won't affect that status, however, even if it drags their Will up above the percentage point that triggers the given status. It's not a quick fix once someone is already unfit for combat.

 Focus PCSes also benefit notably from the introduction of what I call the phobias system, as phobia triggers are actually Will tests; a soldier with a Fear of Sectoids can be made less prone to Panicking when encountering Sectoids by slapping a Focus PCS onto them, that kind of thing. This isn't a great solution, but it can be a useful bandaid solution until you get the Infirmary online to start on therapy for a more permanent solution, which is much better than the base-game situation of 'no, seriously, what use are these?'

Perception
Adds Aim to the soldier.
Basic: 4-6 (5-8)
Advanced: 7-10 (9-13)
Superior: 12-16 (16-21)

Perception is notable for the fact that it applies to secondary weapons in addition to primary weapons. This means Sharpshooters, Rangers, and Skirmishers all 'double-dip' on Perception's utility.

 Templar don't, because their melee attack is unable to miss, so it only benefits their Autopistols. If you happen to get a Templar whose X-COM skills are all about specializing in their Autopistols, you might want to give them Perception, but for most Templar a Perception PCS is wasted on them. Give them one of the others instead, any of the others.

 In War of the Chosen, late-game Rangers don't care as much unless you double up on Rangers in missions, since the Katana can't miss and it's the obvious default to equip your Ranger with once you've got it. More debateable is the Alien Hunters DLC affecting Sharpshooters, since the Shadowkeeper has an innate Aim boost that can readily lead to 100% accurate shots, particularly in conjunction with Aim climb benefiting it.

 Overall, though, Sharpshooters are the most consistent class about appreciating the Aim boost, since Sniper Rifles can only ever lose Aim from their internal Aim modifiers; where other weapons can compensate for having less than 100 base Aim on a soldier by getting closer, the Sniper Rifle is stuck with height advantage, innate Aim, and universal effects like Holo-Targeting. And even once a Sharpshooter is over 100 Aim, every 2 points of Aim past that is another tile of Squadsight they're completely accurate out to.

 More subtly, Sharpshooters are the class that's most consistent about ending up shooting at enemies that are in Cover. Not only do other classes have their Aim climb for getting in close, but they're vastly more prone to flanking, and so don't need as much Aim support to overcome Defense. (Outside, of course, enemies with high innate Defense, such as Archons or Gatekeepers) Particularly if you're fond of trying to leverage their Sniper Rifles, Sharpshooters get a lot out of Perception PCSes.

 Skirmishers appreciate how Perception PCSes affect Wrath, Justice, Whiplash, Reckoning, and even Retribution. Whiplash in particular is tuned so that a Skirmisher can't reach a 100% chance to hit without high ground or Aim boosting, and it's sufficiently precise that taking high ground with no other boosts will still result in a miss chance against anything that has innate Defense, even at max level. It's not unreasonable to argue that they actually get more out of Perception PCSes than Sharpshooters do, at least once you're looking at a mid-to-high-level Skirmisher.

 The next-most consistent class about appreciating Aim PCSes is probably Grenadiers who have specialized in shooting things instead of Maximum Grenade Action. They do get a skill that straight-up hits regardless of Aim, but overall they tend to be almost as bad as Sharpshooters about firing on enemies in Cover; for one thing, part of the point of Saturation Fire is to try to wipe out Cover. Also notable is Chain Shot penalizing Aim and making getting the second shot dependent on the first shot hitting, raising what such a Grenadier considers an ideal Aim value. And Demolition does actually benefit from Aim boosting once you're past 80 Aim, so that's an unusual bit of utility to boosting Grenadier Aim, albeit one that won't apply for a while thanks to Grenadiers gaining so little Aim from leveling; a Basic Perception PCS that doesn't roll its maximum value won't help Demolition at all even on a Colonel unless you have Integrated Warfare. (Ignoring the possibility of having gotten Aim out of Covert Ops in War of the Chosen) Similarly, even an Advanced Perception PCS won't necessarily improve the odds on a Grenadier the second they have Demolition; only a Superior Perception PCS is actually guaranteed to help with Demolition's chance of success.

 Psi Operatives are probably even worse than Templar about Aim PCSes being wasted on them. While Psi Operatives don't ignore their gun entirely, especially if you prefer to send them out when they're still low in level instead of just sticking them in a closet until they're maxed out, they are still heavily biased toward spending their turns on their special abilities, none of which benefit from Aim. The main reason you might consider giving them Perception anyway is that there's not really any PCS type that strongly suits them -I prefer Speed on Psi Operatives, personally, but it's not like there's no merit to being able to count on their gun for stuff like finishing off enemies so you can save their abilities for later, instead of Soulfiring because you have an 87% chance to hit and missing would be catastrophic and then immediately wanting Soulfire again while it's still on cooldown.

Agility
Adds Dodge to the soldier.
Basic: 10-15 (13-20)
Advanced: 15-20 (20-27)
Superior: 20-25 (27-33)

Dodge is a new defensive stat to XCOM 2, and feels like it was intended to be something of a third defensive lane or type, but unfortunately doesn't stick the landing.

 Dodge's actual effect is that it's a percent chance to halve an incoming attack, rounding the damage down. (ie an attack that does 3-4 damage hits, and your Dodge roll triggers: if the damage roll was 4, you instead take 2 damage. If instead it rolled 3 damage, you halve it to 1.5 and then round down to 1) Additionally, a successful Dodge roll overrules a crit roll, preventing the crit from adding damage. (Exception: Rupture's forced crit is exempt, though the crit damage will still be halved) This is especially important due to how crit chance works in XCOM 2, but that's for another post: for the moment I'll say Defense is less protective against crits than it was in the prior game.

 This has a pretty obvious interpretation: Defense protects against low-accuracy attacks, Armor protects against low-damage attacks, and Dodge protects against high-crit attacks.

 Unfortunately... for one thing, this is another example of the unevenness/inconsistency thing I covered in the War of the Chosen Grenadier analysis post; Defense and Armor protect against attacks based on their weak areas, where Dodge protects based on their strong area. For another, Dodge is random: it's not that 10 Dodge ensures most enemies need a flank to have any possibility of critting, it's that 10 Dodge means 10% of successful attacks that would otherwise be crits won't. For a third, the fact that it halves damage in general muddies the water, making it less an anti-crit tool and more a fairly general defensive stat that happens to be particularly notable against high-crit attacks. For a fourth, crit specialization isn't really a mechanic for enemies; sure, some enemies have more crit damage proportionate to their base damage than others, but crit chance on enemies virtually never ranges outside the 0-20% range and flanking is basically the only way enemies have to get their crit chance higher. For a fifth, Dodge is completely negated if an attack has a 100% chance to hit.

 It's worth noting here that this last behavior is a significant patch change, but the original version isn't really any better: originally, each point of Aim over 100 canceled out a point of Dodge. (ie a 105% chance to hit would mean a target with 10 Dodge only has a 5% chance to Dodge, whereas a 110% chance would reduce that 10 Dodge stat to a 0% chance to Dodge) Among other points, this meant that Shotguns -the weapon most leaning into crits in XCOM 2- easily ignored Dodge anyway; a point-blank shot from a Colonel Ranger with a Shotgun would end up with an effective Aim of 131, assuming no Perception PCS and no Scope and no Holo Targeting. Before Alien Rulers came along, only Vipers exceeded 25 Dodge (And would end up with only 2 Dodge when faced with the prior situation), and only two enemies -one of which was a limited-quantity boss enemy- got to combine enough Defense and Dodge to still have a Dodge stat in the face of those conditions. And if you happened to have an Aim boost for some reason or another, such as a Perception PCS to let your Sword strikes hit more consistently, or a Holo Targeting from a prior attack... even those enemies could end up with no functioning Dodge, entirely incidentally. Among other points, this still had the jank that Dodge was a counter-crit stat that was then countered by Aim boosting, it was just more granular in its nature. Seriously, why does Aim boosting cancel out Dodge?

... okay, this confusion I'm expressing is probably inaccurate/unfair, given my understanding is Dodge 'fills in from above', but I'll... explain that in a couple posts, specifically in the first Primary Weapons post.
Anyway, nor does the game really lean into the possibility of these specializations. There is not, for example, an enemy that fires twice when attacking but with individually weak shots, such that having decent Armor is unusually beneficial, or an enemy that eg is guaranteed to crit on a flank and has very high crit damage but poor non-crit damage such that Dodge is unusually useful against them, or an enemy that has high damage on its attack and perfectly good base Aim but counts each point of Defense on the target thrice so that being in the open is a guaranteed hit but High Cover is perfect protection even with a high ground bonus.

 This stuff applies somewhat from the opposite direction, where eg a Sharpshooter leaning into Pistols suffers badly against even relatively lightly Armored targets due to their offense being made of multiple individually weak attacks, but only somewhat.

 The overall result is that Dodge... exists, and can be very frustrating when eg it saves a Viper you were expecting to Death From Above or trigger Implacable and Untouchable off of or whatever, but doesn't really fill any particular niche in the game's actual design.

 I'm hoping XCOM 3 either does away with it entirely or manages to actually conceptualize it as something meaningful and interesting. Certainly, the mod scene hasn't made any effort to make Dodge into a distinct and meaningful stat -even Long War 2 instead turns it into, essentially, a second-line Defense stat! Alas.

 All of this means that the Agility PCS itself suffers from being unclear in its utility. It's a survival enhancement for your soldiers, but who do you give it to? Who benefits most from it? How does it compare in utility to Conditioning?

 It's probably best put off on soldiers you're worried about being flanked or otherwise caught out in the open, so basically Rangers and Templar, but you certainly shouldn't count on it to save them if they get flanked. Personally, I also prefer to stack Dodge -I give Agility to Templar in part because Focus Levels innately give them Dodge, and higher Dodge means much greater odds of it doing something. By a similar token, I usually prefer to designate a (Non-Templar) soldier as being the one I send anytime I have a Dodge-boosting Covert Op I want done. This usually means a Ranger, and in turn I usually equip that Ranger with light armor. (Spider Suit/Wraith Suit/Serpentsuit)

 But the whole thing is fuzzy and the only reason I don't consider Agility a hard pass on using at all is the nature of PCS looting means you don't necessarily have a better alternative. If I had my pick of PCSes, I would always kit out my Templar in Speed PCSes, for example.

 The one exception to all this fuzziness is that reaching 50 innate Dodge is the point at which Hunkering Down will bring you to 100 Dodge, and thus ensure anything that has any chance of missing will be Dodged if it hits. It's too bad Hunker Down's bonuses don't apply against flankers, because otherwise this could be used to save a soldier from a flank. As-is, it's basically a point of trivia.

 One final weird, essentially invisible note about the Dodge stat: it's actually ignored if the attacker is Concealed. Since the game provides no feedback on Dodge on enemies by default, there's no way to notice this on your own without either a mod displaying Graze chances or just playing a ton and at some point noticing you never get a Graze on shots from Concealment. This is essentially irrelevant on the player's defensive end, as no enemy is willing to attack from Concealment... excepting the Assassin being willing to do so with her melee strikes, which ignore Dodge no matter what, so it still doesn't matter.

 Offensively, though, it means you should prefer to open Overwatch ambushes by having the initiator shoot an enemy with Dodge if there is one (The Overwatchers in the ambush will not get to ignore Dodge), makes Reapers unusually good choices for risky shots on Codices because they'll either miss or do full damage, no possibility of a Graze, so long as they're in Shadow, and gives a hidden bit of utility to Phantom and Conceal. This is particularly relevant to the base game, where Phantom may be thrust upon one of your soldiers by the Advanced Warfare Center and you should try to make the most of it, but even in War of the Chosen you should keep it in mind when taking into account Sitreps, or if eg you have a Savant Ranger and Art of War and find yourself running out of skills to buy such that you might as well at least buy Conceal.

 Also, to be clear this is specifically the attacker being in the Concealment state. This isn't like how Shadowstrike triggers if the attacker starts the attack unseen by their target: a Ranger can't avoid Dodge chance by Slashing from around a corner, nor a Sharpshooter by firing from beyond sight. Nor is it defined by the enemy's readiness state; alert enemies will still have no Dodge chance if their attacker is Concealed.

 It's a weird detail the game never hints at and that's virtually impossible to figure out on your own, though it makes a certain amount of in-universe sense given Dodge seems to be intended to be literally the victim... well, trying to dodge. Can't dodge if you don't know the attack is coming, after all.

Conditioning
Adds HP to the soldier.
Basic: 1 (2)
Advanced: 2 (3)
Superior: 3 (4)

Toward the beginning of the game, Conditioning is an excellent choice to put onto anyone. Even one HP is a fairly obvious boost in survivability relative to low-level, low-tech HP values. (Too bad you can't give PCSes to Rookies...)

 Later in the game, it becomes harder to justify. Colonels in endgame gear aren't far off from 20 HP, and the serious threats hit so hard going from, say, 16 HP to 20 HP doesn't necessarily help at all. A Sectopod can one-round such a soldier either way. ("But what about Armor" I hear some of you wondering. I hope you're talking a Blast Padding W.A.R. Suit-wearing Plated Vest-carrying soldier, so they have 21 HP and 4 Armor: the Sectopod's 2 Shred will work out to it doing 6-7 damage followed by 8-9 damage; at that point you actually can survive even with a crit, as it'll do 18-20 damage, leaving you barely alive... oh, but if it rolls two crits you're just plain dead) 

 That's a particularly extreme scenario, but it's generally the case that even a Superior Conditioning might save a soldier, or it might be totally worthless. Particularly problematic is that the obvious classes to give it to tend to be more interested in other PCSes.

 Late game, Specialists are probably the best class to give it to; they don't need boosted Mobility to do their core jobs, and several of their abilities don't care about Aim, and in the case of medical Specialists it's particularly critical that they survive so they can patch up everyone else. In War of the Chosen, Focus is worth considering for them instead in hopes of maybe warding off Mind Control/Panic, for much the same reason of ensuring they're actually in a position to save people when things go wrong, but Conditioning still doesn't really have better soldiers to go to.

 Personally, I feel like Conditioning should've provided Armor. At the exact same values it would've been a lot more meaningful; an early Advanced Conditioning that gave Armor instead would make the lucky soldier take only 1-2 damage (Up to 3 if they crit) from basic ADVENT Troopers, dramatically improving their survivability (Where currently a Legend Squaddie getting Advanced Conditioning is going from 5 HP to 7. Not guaranteed to be two-hit-killed by an ADVENT Trooper, sure, but still very likely to be two-hit-killed, so who cares?), and it'd be relatively natural to slap Conditioning on troops you intended to put in heavy armors to maximize their Armor. It wouldn't even be a broken, abusable strategy -a surprisingly large number of enemies have Shred on their primary weapon, or present hazards that don't care about Armor at all, and pity damage would ensure that when dealing with the handful of enemies that genuinely couldn't cope with high Armor you still couldn't get away with standing in the open and taking it.

 Sure, the PCS concept doesn't naturally lend itself to justifying Armor boosts in narrative/conceptual terms, but it's not like it lends itself to justifying HP boosts any better. I have a chip in my head, so a bullet that would blow someone else's head off magically fails to kill me? Why, exactly? Boosting Armor wouldn't actually make less sense, conceptually, than the current benefit, while being vastly more interesting and meaningful on the gameplay level.

 Mind, this is part of a broader thing of XCOM 2 being overly-cautious with the Armor stat, particularly for the player but also when it comes to enemies. I even understand why the devs would want to be cautious with Armor.

 But I'm still hoping XCOM 3, if it straight-up ports the PCS concept, either goes with more generous numbers or replaces Conditioning's HP boost with an Armor boost.

Speed
Adds Mobility to the soldier.
Basic: 1 (2)
Advanced: 2 (3)
Superior: 3 (4)

Speed is good on any class, of course, but it generally provides the highest value to Rangers and Templar by extending their melee strike zone. Rangers and Templar with the Reaper skill particularly appreciate the ability to bounce around in whatever order most efficiently utilizes their declining damage, but in general it's great for them.

 Alternatively, it can be worth considering putting on Sharpshooters so they have an easier time keeping up with the group, particularly if you like to bring them onto timed missions but still like to use them as Sniper Rifle specialists instead of Pistol specialists. I don't think this is a particularly great use of a Speed PCS, but it's not bad.

 Reapers are also an interesting possibility since Shadow is a multiplier of their base Mobility. It's only a 37.5% multiplier, but that still means a Superior Speed or boosted Advanced Speed will tack on an additional point of Mobility outright. I'd generally rather give a Speed PCS to someone else, since Reapers are very capable of pulling far ahead of the group for several reasons and don't really need more Mobility, but there's worse ways you could use a Speed PCS, and if your run has an unusually large number of them... why not, at that point?

 In a bit of a reversal from the prior game, where Supports had a desperate need for speed to do their core job, Specialists are probably one of the soldiers who least appreciates Speed PCSes. Their support duties don't require line of sight or line of fire on allies, while their offensive effects are quite generous in such regards, and if you take Ever Vigilant even a turn spent Dashing to catch up with everyone still results in them being ready to take a shot.

 The remaining classes come down more to playstyle and judgment call stuff. A Salvo Grenadier, for example, can be argued either way; on the one hand, if they're spending combat turns not moving at all, it's not helping, and approaching/flanking doesn't benefit grenades or Heavy Weapons. On the other hand, more Mobility means it's easier for them to keep up with the group in spite of their fighting style leaning away from movement, and also makes it easier for them to find opportunities to use their cannon to contribute instead of having to burn up one of their limited-use attacks.

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 Curiously, there's a complete image file for a Psi-boosting PCS:


 This would admittedly be a bit silly, as only Psi Operatives would get any benefit out of it and their stats are already tuned so that a maxed-out Psi Operative doesn't really need any further Psi, but it's still a bit surprising to see that they got far enough to make a complete graphic before... deciding it was pointless or whatever happened there.

 It's also a bit frustrating, since Psi Operatives are left with no particularly good PCS options as a result.

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I like the idea of PCSes, a tool for customizing your troops and an alternate approach to making it so that looting your enemies' stuff is part of how your soldiers improve, but the execution of PCSes in XCOM 2 is very lackluster. Perception is unequivocally the best of the PCSes, Speed is second-best, and the rest just kind of exist and don't have clear roles. You might as well plug them in anyway if you loot them, as it's not like they sell for a ton of Supplies, but they don't fill niches in the game or anything, they're just sort of... existent.

 Thus, it doesn't really end up being a customization system at all, and the benefits as far as loot-based improvement are pretty narrow. It doesn't help that PCSes are acquired disproportionately from Supply Raids, where you're already getting piles of loot to boost your troops: they end up a bit drowned out in the midst of you getting the resources you need to buy the latest gear and whatnot, particularly in the base game where a competently-run campaign doesn't necessarily need more than 6-9 soldiers across the entire run and thus rapidly stops caring about the intermittent basic and advanced PCSes being semi-regularly dropped by enemies. 

 I'm particularly puzzled by the nature of the benefits selected by PCSes. The general shape of the concept really suggests a way to gift skills to your soldiers, which would've been an interesting way to make high-level soldiers less crucial and open up all kinds of interesting choices, where stats being provided is just plain mystifying from a chip in your skull. Admittedly the question of 'what happens if you give a skill PCS to someone who already has that skill?' would be a problematic one, but that could've been sidestepped in any number of ways, such as making PCSes provide skills not normally available to classes.

 Ah well. PCSes are also a novel system, so it's not surprising the game didn't get them perfect.

 Next time, we cover Weapon Attachments.

 See you then.