Zidane - he can use Dyne

Vivi - He can use double magic

Dagger - Her summons summon again and again

Stiener - His attack is stronger

Freya - He does more damage when he jumps. (He'll stay in the air and throw spears down

Eiko - she can cast double white magic

Quina - She has a better chance at eating an opponent.

Amarant - I think his special powers has an all effect.