Well, I can only speak about MAMECE, because thats what I have installed on my Axim. Its got about 100 games, all of them rather old (newest game is 1943), and these all run extremely well. In fact, some of them have to be underclocked in order to be playable........
The best platform for MAME is.......the PC of course!!!! All games run, and 99% of them run perfectly

A friend of mine has all but 3

roms for the latest MAME, and I intend to leach it of him
Anyway, if anyone else has any luck making MegaMAME to work, please share the info......I tried the trick with the memory bar, but no luck.......