WoL=Alternate. His normal's not bad, though.
Garland=See above.
Firion=He looks like a 'tard in his alternate. Normal.
Mateus=I like the gaudy emperor look of the normal sometimes, but most of the time, I prefer the alternate.
OK=Alternate.
CoD=Normal. The alternate kind of looks like shit.
Cecil=Alternate.
Golbez=Probably normal, if I played as him. I'd have preferred his alternate if it chilled the fuck out with the Shoulders of Doom.
Bartz=Normal. DEFINITELY normal.
Exdeath=Normal, I guess. They look about the same, but his alternate bothers me in some of the darker backgrounds.
Terra=Alternate. In fact, when I unlocked it, I went, "Fuck yeah, green haired Terra!"
Kefka=Alternate.
Cloud=It's weird. His alternate attire is bland, but his normal attire has bland attacks. I prefer the First Tsurugi to the Buster Sword, but the Ultima Weapon to the...whatever.
Sephiroth=Normal, although fighting people with swords & crazy magic & shit without a shirt would be totally badass.
Squall=Normal. The SeeD uniform isn't as bad as everyone says, but...eh....
Ultimecia=Would depend on my mood if I played as her.
Zidane=Alternate, I guess. Probably would depend on my mood, if I played Zidane.
Kuja=See above.
Tidus=Alternate. I hate how weirdly dark his "normal" outfit is.
Jecht=Either works, I suppose. I slightly lean towards normal.
Shanttoto=Alternate, I guess. I don't really like Shanttoto period.
Gabranth=Alternate. I like the red aura of the normal, though.