I know pretty much nothing about either of these guys other than they're rather quite good at the boxing lark. I do know Mayweather tends not to get hit, and apparently the fights are pretty boring and end in a decision win. However I also thought Mayweather retired years ago for some reason.
I would've gone with Mayweather, but all he's talking about is money and how he doesn't like boxing, it's exactly the kind of thing I see people pointing out if he were to get knocked down, and in documentaries people saying "he didn't have the fight in him, and you could tell he was gonna lose".
I'm assuming Mayweather isn't smart enough for everything to be an elaborate mind game to try and get Manny complacent. Pretend you're a prima donna who doesn't want to be there, give a ****ty first round, then BAM surprise mother****er.