If it actually got as far as blows, Face would probably win. Why? Well, on the face of it (heh, pun), Face was just a pretty boy whilst Starbuck was actually the sort to get his hands dirty. However, I reckon Face is a bit of an American Psycho and beneath his take-home-to-meet-your-mum exterior is a raging sociopath.
Face has more punch up experience. He would wouldnt he? Would you fancy punching a Cylon? Maybe there should be a number of trials to decide the winner. A driving competion a pilotiing competition, a shooting competition, some classic fisticuffs competition & a pulling competition like the ones young lads have in Ibiza.