Damn that's a tough one! Oscar would really depend on his left hook that was his bread and butter. When Titio threw that left hook, it really changed the coarse of the fight. I give a slight edge to Oscar though, he is a natural southpaw that happens to fight orthodox.
Tito's left hook was fast AND freaking powerful, just ask Vargas who had never been dropped in his young career before fighting Tito. He fights Tito and suddenly BOOM! 5 knockdowns (many were by left hooks)