I think I'm the one confused lol I was kinda hoping you could inport a rom file only once regardless of platform I guess. So, say, blazstar.zip is only included in the Neo Geo platform even tho it's in the mame romset too. That kinda thing.
I use retroarch for both mame and fba, so video quality is about the same, I just find FBA to be smoother, oddly. Probably placebo.