PSP Vita's games are pretty good however they can't be hacked yet so you still have to buy all the games. However the 3DS already has an R4 which has came out so you won't actually need to buy the games.
So it depends on if your willing to cough up some cash for some pretty good games or not pay much for decent games.
I myself would choose the 3Ds cause I'm a cheapo like.
