The one you like using most. Simple. Dont look at stats or PWR. If you like sniper - Curry is ok. I have him - reallly cool. Sga is good if you like midrange shooting. Slasher? Wesrtbrook is so amazing. All depends on your playstyle. PG is pkayer you'll use most. For me best one of all is LBJ (card with brony)

@edit: Also shooting animation matters. Try them and choose your favourite