Sugar Ray. Better technique, better speed / velocity of his punches, and more power in a pound for pound sense.
If you notice where Hagler is pressed to end a fight, he does so quickly. It doesnt have to be ONE punch, he just has to end it within seconds. This was the case against Scypion when WS closed the distance and got in his chest. Marvin regrouped and took him out with a right left. With Hamsho, Marvin was pressed becuz of the butting so he ended it by putting more snap on his punches which quickly took the life from Hamsho in round three. Two lefts followed by two rights brought him down. Same situation in the Hearns fight when time was called and Hagler ended it seconds later