I'm not really a fan of either fighter but my unbiased prediction would be Mayweather by decision. Pacquiao is the more powerful but sloppy fighter, while Mayweather holds the speed advantage and is the more accurate puncher. Mayweather has the much better defense, and the better chin also, and I believe he has never been knocked down, compared to Pacquiao who has been knocked out twice.

Comparing common opponents, Marquez gave Pacquiao all he could handle in 3 fights (arguably winning two of those three close fights), while Mayweather easily out-classed Marquez, winning every round of the fight.