I own both MMr and AFMr. I've had MMr for a year now, AFMr just showed up at Thanksgiving. Both are good games, but for me MMr is the better game. Better humor and callouts and bit more to do. AFMr is simpler, but definitely different enough. They are NOT that similar, the ramp shots aren't the same by a long shot. I will say that CGC knocked it out of the park with AFMr, i have LE and that topper is crazy awesome and the big screen, OMG. I will instantly purchase the screen upgrade for MMr as soon as CGC releases it.
I have played MB a fair amount but haven't owned it, I don't think it's good at all, not impressed with it enough to go buy one. MMr as soon as you play it, it's like ok this is fun as hell. Whether you have a crap game or a great one it's just a blast to play, that's what makes it a good game, it has a TON of replay-ability (is that word?).
There is a reason that both are in the top 5, you really can't go wrong. I think most people will agree MMr is the better game, but you'll have a few that prefer AFMr, which is totally fine.