Yeah trunks is definately the worst, I never see anyone play as him probably cos of his extremely weak attacks and finishing burster is easy to dodge. I hope he is greatly improved in beta 2 so people actually use him!
I have equal favourites buu/piccolo but if that gets boring i chose random (I'll chose again if i get trunks!!!)
I like buu more because of his candy attack.
eg. Guy swoops at me I block it, teleport up, swoop straight down, smash them on there ass and turn them into candy while they're down
O yeah by the I haven't heard this mentioned yet but it seems:
Donut= 100,000 more power (or 10 000, I forget)
Chocolate= Refill ki
Cookie= Refill Health
I'm pretty sure thats how it works, it does for me anyway (correct me if I'm wrong) of course i always choose donut.