The Front End is subjective. So, I'd try them out and see what you think.
By best version of MAME I'll assume you really mean version and not flavor (i.e. MAME vs MESS vs etc..). Honestly, I'm not sure of the best. The devs have done tons of work refactoring the code base and adding new games. If it were me, I'd go with the latest version with two exceptions: 1) if the game is broken (it might be fixed with an update, so check on that). 2) for 3D games (i.e. Gauntlet Dark Legacy), I'd use an older version of MAME as the older version (0145 or 0159, damn I need to get this straight in my head) are faster for those games than the latest versions. Given your hardware you can still probably run those games with the latest version of MAME at full speed anyway, but the older version still seem to be smoother.