Okay, some run down on the PCs so far. (I'm through the Shinra Mansion, haven't opened the safe though.)
A disclaimer: who I actually used tends to be a combination of who I think will be effective, picking entirely randomly via dicerolls, and asking others in the room for suggestions (which in turn tends to result in me using Tifa).
All comments so far exclude Vincent and Cid, and will mostly exclude Yuffie since I got her late*.
*late = the first time she isn't a freaking 6.25% encounter
Cloud: One annoying consequence of the (very welcome) increase in PC differentiation is that it's now much more annoying to be stuck with Cloud. I think this would be true even if he were still the best PC, but instead he does feel somewhat nerfed. It feels like Cloud gets very few niches over other PCs.
-His physical game is typically kinda underwhelming. He lacks Tifa's crits and Red's weapon variety, as well as Barret and Yuffie's long range. It's capable and there is definitely tradeoff between back row and front row for him, which I suppose is fine.
-His magic is decent but not as good as in vanilla FF7. He gets a decent number of materia slots; his weapons should place him as #2 at this, but he misses out on key armours like the Four Slots and Platinum Bangle; if you miss the Shinra Beta he'll be 2 slots on armour behind everyone else except Tifa (until Corel) and Barret for a significant chunk of disc 1. As for his raw magic stat, he went from being essentially tied with Aeris for the top spot to #3 behind Aeris and Vincent, and I don't find his paltry MP edge makes up for that.
-Finally, his limits don't really impress. They only do damage, and they're row-subject, so if you decide to make Cloud a back-row caster type the L1's become super-underwhelming (and at 120 kills he's stuck there for a while). Against enemies vulnerable to paralysis a Cloud limit pretty much became "meh. Whatever" which is a terrible feeling.
Despite the fact that he's not terrible (in particular he's not bad at anything), Cloud does feel a touch underwhelming and it's made worse by the fact that he's forced. I'm not proposing you just uber him in a huge way, because I really like other PCs having niches he doesn't (e.g. better physicals, better magic, lots of HP, unique limits, etc.). If you just make him the best mage or the best fighter, well, that devalues the other PCs who are supposed to excel in those roles (especially because at this point in the game, there's only one Earring and only one Power Wrist).
But I feel like he needs a push somewhere. A couple possibilities:
-Improve his limits. Make me excited when Cloud gets a limit. Either let Braver ignore row or increase its multiplier. Increase Blade Beam's shockwave multiplier. etc. To some extent this is also Tifa's niche, and she should obviously win front-row damage when the player lines up the YEAHs, but Cloud being good at this too and in slightly different ways (reliability, targetability, long range) would be nice.
-Make him good at having linked slots. One thing I'm finding is that I often don't have the linked slots to use all the blue materia I'd like. Blue materia is cool! Cloud is supposed to be an expert in materia, and would probably know his way around it. Give him more linked slots on his weapons in general (particularly the Force Stealer) which would give him an edge over Aeris, who has more slots and more blasty power.
Barret: Barret has big HP and decent enough strength and long range. This is cool! Mind Blow might be able to cheap things out, but it hasn't really come up for me.
To pay for this, Barret has crappy magic. He also has few materia slots; his weapons don't provide many, typically, and he misses out on the better armours in this regard. Those are pretty notable weaknesses. And finally, he misses with his physical sometimes. Early in the game when Assault Gun is great this is fine but later on his power lead varies and it just feels like an annoying weakness that other PCs don't have to deal with (including Yuffie, so it's clearly not just a long-range balancer).
I don't end up using Barret much, as a result. I think he has a place, with his long-range physical damage (when he's stuck in short range he feels rather trashy, a bit more HP/non-crit damage than Tifa doesn't excuse everything else). I certainly don't think he's a terrible PC. But he's not someone I use super-often anyway.
I'd scrap the sub-100% hit and improve Atomic Scissors in some way, and I think that would basically fix him? Just remember that any stretch of the game where he's screwed over on materia slots, you need to have him make up for it in some other way, and a decently powerful back-row weapon seems like the only way to do it. (or a lot of enemies weak to shot I guess)
Tifa: I'm happy with Tifa. The 40-60% critical rate is an interesting niche. She doesn't have that much raw attack (high str but weak weapons) but criticals and great limit mulitpliers (though with risk) easily make her one of the best at that side of things. She wants to be in the front row but that fits with her wanting to get limits, and has enough HP that she doesn't feel like a glassy liability.
Her magic and materia slots are on the lower end but not terrible or anything, which fits pretty well. Since Barret is ranged and has even more HP I'm fine with him being worse at that.
The main place I moved a bit away from Tifa use is after Red gets the Seraph Comb, because that thing is amazing and makes me really want to concentrate on him as the fighter for a bit and give my other party slot to a mage. But Tifa still has better limit damage and more bulk, and it's perfectly reasonable to run both.
Aeris: Works as intended. If you're gonna have a temp in this system, better make her good. Magic! Does the job. Materia slots! Fairy Tale is great. Weapons which give Vit/Spr are interesting but feel like they miss the point a bit although they do have more linked slots so hey I guess you could run utility Aeris with one.
Limits are different in a lateral way, no way to pump out damage is bad but Seal Evil rules randoms and limit healing's value increases considerably with other sources of MT healing greatly limited, so I'm never gonna complain about them as an option. And since I just got it, thank you THANK YOU for fixing Breath of the Earth into something I actually want to use.
Anyway I use Aeris periodically when the mood strikes me and she works pretty well. She has clear weaknesses on lack of damage limits and poor HP but she's always a reasonable choice.
Red XIII: Man, his stats are just excellent all-around. There's not much to dislike about Red; his only bad stat is HP and even then he's only like 10% behind Cloud. (No, base vit/spr still don't matter.) Every weapon gets a different element! Find one which hits a weakness and watch an enemy hit by it explode. FF7 elemental weaknesses aren't that common so this isn't as OP as it could be, more neat. But regardles, he's the #2 mage and in compeition to be the #2 fighter. And he gets a MT haste limit which is amazing prior to getting Time.
Seraph Comb is still terrific on power when you get it, which is plot-appropriate so that's fine.
Just about the only negative thing to say about him is being row-subject limits his offensive potential on limits. Often enough I even use Lunatic High in randoms...
But yeah, if there's a PC who's in some danger of being too strong it's probably him. He reminds me a lot of vanilla Cloud in that he's better than most PCs at most things... not always the best but very strong overall. But since he isn't really the best at anything (barring base physicals for a window post-Seraph Comb?) maybe I shouldn't be too concerned because the ~powergamers~ may gravitate towards specialists.
Cait Sith: Is. Freaking. Weird.
I dunno what I expected you'd do with him. Good magic, bad speed, good HP? Exaggerate his existing stat build, in other words. When I first realised his magic was trash I had no idea what to make of him. And indeed he's kinda underwhelming in Corel Prison, although HP/MP keeps him from feeling awful.
But yeah pretty much every other weapon gives him some sort of weird unique niche. The White Megaphone has huge power for the time, but randomly adds Haste? Interesting synergy with Dispel; I'd have used it, except that Dispel is IMO too pricy on MP (you're already sacrificing a materia slot for an extremely situational spell, guys). It's light on materia slots so you kinda have to use it for this. Green Megaphone does gravity damage? Seems like it'd be quite potent if you twinked his Str, assuming that works, from the description (free 62.% gravity with a Power Wrist?). Black Megaphone does... magic damage? I've not experimented with that one; kinda curious. And then the Silver Megaphone does fixed 320* damage, pretty cool at my point though will obviously fall off, and its row-ignoring so that's cool.
*The in-game help claims it is 360.
Oh yeah and Dice is a pretty potent limit at my point, though that is definitely falling off.
I haven't actually used him that much but he definitely does look rather cool. And he tends to get enough materia slots/MP to run utility setups well, which is nice, so he isn't entirely about his gimmick.
Gonna pass on Yuffie comments for now.