A buddy of mine finished street fights with one single jab to the nose. He's very fast and hits hard. An accurate hard jab does wonders on the street, where you deal mostly with untrained fighters.
I box and have done Wing chun. For self defense I would pick boxing, no question. Ducking, slipping and rolling confuse many thugs and open up opportunities that I just don't see in Wing chun. Of course, for an actual self defense situation I would use elbows, low kicks and knees, whatever is needed. But boxing would be my base.