Yeah, but the fact that they have such different backgrounds might end up making for a really good match.
Yeah, they may be from different backgrounds, but the fight will be fought in Mayweather's discipline... and that's a huge advantage. None of the advantages of McGregor's MMA background will be of any use in a pure boxing match. I mean, a chess grandmaster and a checkers grandmaster have different backgrounds, but if it's a chess match you have to pick the chess grandmaster, no questions asked.
edit: I guess you have to say McGregor has "a puncher's chance", and McGregor is a spectacularly gifted puncher.
-k