Floyd @ junior lightweight >>>>>>>> Shane & Oscar at lightweight, or Moorer @ light heavy. (still have not had enough coffee to dredge up any more examples of "guys who are mythical p4p beasts in divisions they didn't linger in long enough to be most closely associated with them" but there are loads I'm forgetting, I'm sure...)
He was a h2h beast at lightweight. So was Oscar. Pound for pound, I'll take super feather PBF over both. In a straight-ahead meeting, though (say Floyd in his 130lb heyday moving up to face the 135lb versions of either) both were probably too much for him with size factored in.
Mayweather doesn't have the ***** to fight like a man i have always said this and get proven time and time again.