Cannot really match up prime for prime IMO, because Chavez peaked in November 87 against Rosario at 135lbs, and Mayweather was either at his best at 130lbs or 147lbs...

But I take Chavez to win by close decision at 130lbs, and to win a lot easier at 135lbs by decision.

Mayweather to edge a points decision at 140, and to win a very comfrotable decision at 147lbs.