Margarito would win because of the conditioning issue. Tony is in his prime and Shane is a natural 130/135lbs. Tony would win but, I can see Shane beating him if he has a good night.
margarito does not ko shane, i even think mosley would win the fight by decision, mosley is tougher than cotto.
I think marg would wear down mosley just like cotto and get a late ko. "IF" and only if marg starts early.