I'd say it comes down to how effective Trinidad cuts the ring off. If he throws a couple of bomb left hooks at Mayweather and he doesn't like the taste of them he's going to go the Hector Camacho route. But if Trinindad doesn't effectively cut the ring off and Mayweather concentrates on staying away from Tito's left he could just pot shot and use lateral movement to win by a wide decision.
If the fight is San Juan, I take Tito. Tito's left hook can reach across the ring to hit you like Vargas and Joppy quickly found out. Vargas was lucky to even get out of Round One, and Joppy said later he had never been hit that hard. Because of Mayweather's smaller stature, his head is at the perfect height to be hit, whether you have to go thru a glove or not. I see Mayweather going down once or twice in the first round, and with the San Juan crowd behind him, Tito chasing Mayweather around the ring for a couple of more rounds laying heavy leather on Floyd until the ref stops it in the 3rd via a TKO.