Actually, niether. Sharpshooter is good for sniping, and DF is good for the guys who dont wanna be confined by cover. If you want a balance between the two go for the Sabatuer.
It gives you the "hot persuit" ability which allows you to - when you leave cover- use cover only abilities. Im a lvl 24 sabslinger and I love it for PvP and PvE.