Since we know for a fact he used plaster in that fight.... The fact of the matter is Cotto hit Margarito with everything and nothing happened. Its the pressure that made Cotto break down mentally. Same result for both fights. If anything fighting Pac at 154 would probably be his best shot. He would have to hope the weight affects Pac because it wont Margarito. However same result. Cottos chin and trading tendencies would lead to his downfall.
the one problem is that there is no way Cotto can perform that way again. He has been beaten far out of his prime. At any point now his chin just won't hold up to very solid punches.
The fact that for those 6 rounds Margarito was putting in good work by rearranging his internal organs, I favor Margarito.
funny smell to that first Cotto vs Margarito fight its tainted a rematch would settle the score, I want that fight. I also believe at 147 and with a real trainer like Steward working on Cottos balance and defense why not have another go at Pac he has the tools.