mayweather should chop his head to make weight :D
Is that you in your avatar? Is there something wrong with that girl? She looks like a downer. (No offense intended, she really looks like she has down-syndrome)
At any rate, Mayweather would win. He'd be too fast, too technically solid, and too hard for Barerra to hit. Mayweather is in a class of his own.
Also, to reitterate for the dozenth time, this belongs in the fantasy fight section.