I think this one may be close for 4 or 5 rouns too, but I think Mayweather will be too accurate and too fast, and quite possibly too strong for Cotto. Mayweather walks around at a bout the 154lb mark, so he can eat as much as he likes for this while training hard and wont have to drop any weight for the scales. I hope its closer than I think its gonna be!
Zab Judah was as fast or even faster than Mayweather when Cotto fought him, in terms of speed I think Cotto can handle that, Mayweathers game is 'timing' and 'distance' and the only way Cotto can really effect Floyds rhythm is with a jab and Cottos jab is very good.
In the end though I just think Cotto is to small and Mayweather has the ability to adapt to whats infront of him with his versatility. I'm not sure just how effective Cotto really is at this weight class either, he's to small for me.
I'm starting to think that this fight might be close if Cotto fights well. I think the racist has underestimated Cotto...big time.