In MY opinion the best character for battles and questing is Warren-he pwns!!! Anyways for soccer and those minigames it's usually the fastest or (if your the goaly) it's the character with the largest attack area.
Haven't played in a long time.. but IMO, Hawk Prem or just Hawk. Fast >_>.
I play for fun and not for competition .
Really depends on what mode, cards and how you use them. I only play dodge, so I can only give comments on that x.x And even in there, different chars = different ways of movement.
For example, Prem shamoo/normal shamoo and prem cream, can't run in dodge. If you are gonna use them, you're safer off walking, more control over them that way. Also, equipping boots on them would make it harder for you to control.
Hawk/xyrho, in dodge, are probably the most easiest to control. Hawk, in my opinion reverses the best, and xyrho, the swiftest turning points and speed. If you can use hawk, you'd most likely be able to use xyrho, but not the other way around.
If you are planning on playing long matches, then go for Lucy/Aurelli, with good healing rates. Both of them are quite fast too. For me personally, I use shamoo, hawk and xyrho, depending on who's on the other team. Also, there are different ways of dodging, once again, dependent of your character of choice.
Fear meh xDD I'm a 100% dodger.(Just a random statement >.>