I currently have both MM and AFM and I can say that in terms of gameplay and overall fun factor, AFM makes a perfectly satisfactory (if not better) substitute at a lower price point.*
*How much longer AFM remains at the lower price point remains to be seen. 
Having said that, looks like the auction has been pulled already.....
Interesting you say that. I remember going to check out an MM at a dealer a few years back. I'd played MM many times of course, and thought about maybe buying one. Next to it was a ratty condition AFM - I'd recently done the playfield swap on my AFM, and it was in perfect condition.
Played the MM a while and thought maybe.. ... .. then gravitated over to the AFM and had a game, then a couple more. Suddenly realised that I was playing a ratty version of a game I had at home, and ignoring the game I'd driven and hour to check out and maybe buy. Decided not to do it.
MM is a great game, but I prefer the theme of AFM. They are comparable games in a lot of respects, a taste thing I think.
