Sorry I took so long to answer
I kinda of forgot to check it.
Anyway, I started with Aqua. The reason was that Terra felt a little stiff, a little harder to move around. Ven was good like Aqua but his voice was kinda meh plus Aqua was described as being best with magic (my personal weak point), so I had to go with her.
And guess what ? I beat the game today! Long story short: AWESOME !
Unlike other Kingdom Hearts games I like every second of it (or about 95% of it) as there are some crappy minigames that you have to play but there are also some good minigames, forced and optional.
I think this is
the best PSP game I've played. Probably when the US version comes I'll give it another go with the other characters.