I was a big fan of Lopez and, in theory, he should beat Margarito decisively. But if you were a fan of Lopez, you know that it is entirely possible that he would decide to limit his fighting to 4 punches per round. Magarito, however, by the way he fights, may not allow Lopez to loaf like that. He aggression might make Lopez fight.
Prime for prime, I'd pick Lopez to blast Margarito. If they had a three fight trilogy, I would pick Margarito to win two out of three fights by flat out out-working Lopez who'd come into the ring stoned
"Jose Luis Lopez" are probably the three most generic Hispanic names on the planet. It's akin to naming someone "John James Smith."