What did each one do better than the other? How do you compare their skillset? What was a strength or weakness that one had that the other didn't? Not a head to head who would win in a fight question.
I've thought over this before, very different style and skill sets, at his finest Pernell was precision in every aspect from footwork, slipping, blocking and punching, nothing was wasted and he didn't have too, very by the book and perfect doing so. Floyd was equally skilled but uniquely different, his movements were more as in his shoulder roll but with it he had to block less and he hit harder. No one could find any fault with his footwork and when younger he could be a greyhound with his legs when he needed to be. Both great.
Floyd had far better discipline in terms of training and taking care of himself year round. If Whitaker stayed in shape and weren’t a drug addict, maybe he would’ve officially beaten De La Hoya and beaten or at least turned in a good performance against Tito. Whitaker didn’t age gracefully in his 30s.
Whitaker had better infighting, more pop and a south paw. Mayweather is slightly faster and maybe a slight higher ring IQ. Defense is about even.
Whitaker was more flashy - showboating a lot, & moved more than Floyd did. He had slightly better reflexes, upper body movement, footwork & athleticism. Floyd had a better defensive guard, stance, technical ability, power, adaptability, physical strength, and offense. Both had good chins when tested & even defense. It's just that Whitaker was more flashy, whereas Floyd was also flashy, but more technical with it.
Pea had more flashier footwork, but he crossed his feet routinely, leaving himself momentarily off balance and open to flash knock-downs. Floyd's footwork was fundamentally more sound.
Mayweather was better offensively. Slightly more power but also a tighter punching technique. Whitaker was a better body puncher. For not being a powerpuncher SweetPea scored his share of bodysuit knockeowns. Pea had more agility and uncommon balance. Floyd was technically better and more consistent. Almost like a computer.
Whitaker the better inside fighter, better body puncher and slightly sharper reflexes / anticipation of shots. Mayweather hit harder, kept his shape and form more consistently and was the more accurate puncher. I think any difference in speed was negligible if we're taking them both in their primes. Combination punching, I might just lean towards Mayweather if we're talking his 130-140 best days, although Whitaker underused his own skills in this aspect and could really string them together beautifully as well when he chose to, ala McGirt II.