At welter - and they've both been at 147 roughly the same time - Cotto without a shadow of a doubt. Cotto has fought FOUR welterweights currently in the top 10 (Mosley, Clottey, Judah, Quintana) and gone 4-0. Mayweather, on the other hand, has fought NONE.
If Cotto beat's Pac in Nov. I'd prob have to place him even w/Mayweather. (When taken the Comp over the last years)
As a whole, Mayweather. At WW, Cotto. Who'd win? Mayweather. Who'll go down as the greater fighter? Mayweather unquestionably.
Ill tell you one thing, Cotto has a much better resume at welterweight then Mayweather does despite going up later then mayweather did.... way better.