I've only just started messing with emulation in general so take anything I say with a pinch of salt as it could easily be user error. I spent a while messing about with mame on retroarch while I cant remember which some roms crashed RA when trying to load on some mame cores and not other, whereas all the same roms worked in standalone mame 0.185. With what I am assuming is the most recent core (the one with no number) some games also seem to have audio problems that they dont have in other cores or standalone. One I remember specifically is X-men arcade. There is some crackling in the intro and the music sounds almost midi like is the nearest I can think of but its not quite that. The problem I found with the older cores in RA is that they didn't remember things. For example loading a CPS3 game it would say new CD inserted every time you run the game. I finally decided the best option was to hi-score/no-nag patch regular mame.