I've played with every character in the Japanese version. Tidus kicks ass (he is very very fast and quite strong), Cloud as well, and for my surprise Cecil is a terminator too.
The bottom three are Squall - how could they make so slow and weak??? :angry: -, Sephiroth (he was a disappointment too) and Onion Knight (I hadn't liked him before Dissidia, and it didn't change my opinion).