Henry Cooper's was not too shabby, he decked a pre title Muhammad Ali on June 18 1963, before he was stopped in round 5, due to cuts.
Cooper's left hook was a thing of beauty. Henry wasn't a great Fighter by any means but if I was shopping for a left hook that's the one I'd buy.
With his weight and physical bulk behind it Whyte's hook might be harder but it's not exactly lightning quick is it ? The whip and the snap of Frazier's left hook would inflict a lot more discomfort than Whyte's. Joe was also brilliant at bringing it in from outside his opponent's eyeline. Nightmare.