personally I'd put UME (MAME with all the MESS content unlocked) on and primarily run MAME / arcade titles, but also add a couple of the things that work well for a cab from the MESS side on there too, ones already suited to arcade controls (shooters, platformers, puzzle games, fighters etc.)
that way you're not faffing around configuring multiple emulators, you have a familiar environment set up already just with a bit of bonus content too, most of which will blend seamlessly with the traditional 80s / 90s arcade games in terms of style and player expectations.
that's not going to give you Dreamcast, but Dreamcast alongside what MAME emulates is going to look out of place anyway IMHO. Keep in mind that cartridge based systems tend to work better than CD / Tape based ones for an arcade cabinet because you tend to be able to jump into the action more quickly without load times from the original games.