Warrior of Light: 7/10. Good damage BMS PC once he gets going; takes a little bit but nothing unreasonable.
Firion: 7.5/10. WoL but gets the important stuff considerably earlier making him better. Not as durable as WoL, but better at FMS', so eh, fair trade?
Onion Knight: 2/10. Balance of FMS and BMS, but doesn't get anything to make him stand out. High speed is kind of overkill and there are other PCs who do that, but much better at FMS.
Cecil Harvey: 3/10. Very much the same problem as Onion KNight but not as anemic at BMS'; he's still a case of "really not worth it."
Bartz Klauser: 2/10. FMS Specialists aren't very good, he's not exception, particularly because...
Terra Branford: 8/10. She's just fast enough for purposes of FMS' on top of being actually GOOD at BMS'; game best mage, pretty cleanly, thanks to Trance, Bluff and getting all the essentials.
Cloud Strife: 9/10. And then we have the game best BMS PC due to having what WoL and Firion have *AND* adds an extremely effective limit on top of that. Can be twinked for FMS' if you really want, which could be argued a waste, but hey, at least the option is there and he's still probably better at damage than FMS specialists anyway. I forgot to say, he also gets his good stuff early enough.
Squall Leonhart: 6.5/10. Very much "Cloud-lite"; feels a little less effective than WoL and Firion, but still solid in his own right.
Zidane Tribal: 6/10. Hey look, an FMS PC who doesn't suck at BMS! Has a limit, and can buff the entire team, self included, to be better; his one downside is he does have a limit in his effectiveness due to stat caps, but that's a hell of a lot more than you can say about...
Tidus: 2/10. ...this FMS specialist right here who has nothing going for him. Yawn, moving on.
Shantotto: 6.5/10. A service-able, though overall inferior, variant of Terra, Shantotto is fast enough for FMS', and has all the necessary resources to be an effective BMS Mage, between having all important attack spells, and both Bluff and Dualcast, not to mention a Limit. She's overall worse, but definitely competent.
Vaan: 1/10. An FMS PC who exists solely to horde items...THIS IS NOT A GOOD THING IN THE SLIGHTEST GO AWAY!
Claire "Lightning" Farron: 6/10. A balanced Fighter/Mage, and starts the game with Sinewy Etude, and Omega Weapon is great before pesky Damage caps kick in.
Princess Sarah: 3/10. Workable for a healer character, but she really needs to be placed alongside tanks...
Minwu: 5/10. Like this guy! High HP + lots of defensive abilities and healing, definitely a strong character to have if you just want to SURVIVE the song.
Cid Haze: 2.5/10. Half a point for getting Libra Lv 3, but otherwise *Flush*
Rydia: 2/10. Rydia is some sort of cruel joke, I feel. She gets all the necessary attack spells, but can only use two of them at a time, a distinction Terra, Shantotto and Vivi (the other pure mages) all lack, as well as misses both Bluff and Dualcast, making her overall worse as a mage than Lightning or Ashe. Mana's Paean is nice, I guess, but doesn't make up for her other failings.
Kain Highwind: 2/10. Also a cruel joke, Kain is one of the last PC's you're likely to get, and on paper he should have evrything but can only equip one Pro-active ability, making him significantly worse than many other Fighters. Being as late as he is, he'll also be underleveled.
Sarisa Scherwil Tycoon (aka Faris Scherwiz): 2/10. This character is just kind of a mess; they were trying for some ultra balanced build, and what we were left with is someone who is kind of mediocre at everything.
Locke Cole: 2/10. FMS PC, Libra Lv 2 helps for Dark Notes I guess but that's about all he has going for him.
Aerith Gainsborough: 4/10. Minwu with a few better skills but significantly lower HP, overall losing trade
Sephiroth: 2/10. Very much the same issues as Kain; on paper he's got this really neat allowance for a physical or magic build, but in practice he's gotten too damned late to care.
Seifer Almasy: 1/10. They were clearly aiming for some oddball styled tank here...they failed miserably.
Vivi Ornitier: 5/10. Is Shantotto who is gotten later and without the Limit, making him overall worse, but good if you wanted a 2nd Shantotto or something!
Yuna: 4/10. Aerith variant, for the most part.
Prishe: 4/10. Healer who can do damage in BMS'! This isn't as good as it sounds, because you rarely want to survive if you want to win fights; that said, she's competent enough at the healer thing that she can be a Minwu variant.
Ashelia "Ashe" B'nargin Dalmasca: 3/10. She can do the healing thing ok-ish, and the Mage thing ok-ish, but not good enough at either to bother.
Snow Villers: 5/10. Great tank; lacks healing, but he compliments them well with the really high health and damage reduction.
Cosmos: 1/10. Support character who is gotten as late as Sephiroth and Kain likely *flush*