My experience with the Dreamcast Mame is that it's not very fast. I was trying to play some minimally new games like Double Dragon, Shinobi, Teenage Mutant Ninja Turtles, and it wasn't acceptable. I was using the all-purpose Mame for Dreamcast, however. There are single-game builds that should be faster, but even still they seem to use a lot of frameskip to keep the speed playable, and since I have a PC in my cab that plays everything perfectly, I didn't bother messing around too much. Instead I put the effort into making the Dreamcast play my old favorite console games in front of my TV set (NES, SNES, Atari 2600, 5200, 7800, ColecoVision, c64, etc.).