If you are mainly interested in MAME, Sega Model 2 & 3, and/or Daphne games, I recommend Arcade.
If you are more likely looking to run other systems emulation, HTPC features, and/or Steam, EA Origin integration, then regular GameEx.
Not that I am not promoting Evolution, it's just that Evolution is still in Alpha testing and a bit different when it comes to themes structure, etc. Best to cut your teeth on the more seasoned products IMO.