Mayweather by a close UD. Floyd has the best defense but I think his offense would win this one for him. Pac's left lead is just undefendable and Floyd's defense I think is vulnerable with that punch. his left arm is way down on his belly. I think Pac wins the early rounds being the aggresor throwing and connecting more punches but Floyd is to smart not to adjust and he would be more offensive. A think Pac would go down flash at the middle of the fight. that would be the fight's turning point. Again, Floyd wins by UD but it should be very close.