If the fight between Mayweather vs Cotto/Pac does happen it will be a few years late but either one will be a counter punching masterclass from Mayweather. I see Floyd stopping Cotto late on and getting a UD over Pac. As far as competitiveness goes I think Pac will still be more competitive due to his speed, awkward angles and southpaw style. Whereas Cotto is slower and will be easy for Mayweather to counter.

I don't see Cotto having anything to trouble Mayweather with whereas Pac does. So I think Pac is the more competitive fight for Mayweather.