The biggest "personalities" in a sport are always the ones that do the most for a sport. You can bash Mayweather all you want, but the fact of the matter is, he brought a large audience back to boxing, and if you ask anyone that doesn't even like boxing, "Who is Floyd Mayweather", an alarming amount of people know.
Look at people like Ali, Tyson etc. Big attitudes, love to put on a show and piss people off, get lots of money rolling in.
Back on topic, I think this fight will go to Mayweather too. Mayweather is an insane defensive fighter, which, IMO, has kept his brain in the game, so to speak. The one thing that will give Pac the upper hand is, well, his left hand. It seems like Mayweather's style is extremely strong and structured for a right hander, so it will be cool to see how well he does against a strong left hander.