My cabinet came with MA and I do actually like it. Though there is no support from the original author, there are a lot who know it well. It can be customized [to an extent] but as mentioned, no MP4 support is kind of lame. Over years of looking and experimenting, what I found to the very good converter is Super. At 1st the interface seems odd(?) (cumbersome?), but it's a pretty powerful [and free (sorta)] tool. The batch conversion works great! For me, I didn't care for the audio from the clips. So I simply checked the no-audio box before conversion.
As I discovered (eventually...lol) that for most all games, the are descriptions, box and cartridge art (thinking mostly non-MAME), cabinet picts, controller picts and much, much more out there. XML files are pretty cool! But MA couldn't really take advantage of these they way I wanted (layout/themes).
Over several years I tried many different front ends (Attract-Mode, Easy Interface, Hyperspin, Rocket Launcher, mGalaxy, QMC2...). I was either too impatient to set them up, they were TOO flashy, too simple or just cumbersome. MA is simple and straight forward. The one I finally landed on and like (this month at least..lol) is LaunchBox/BigBox. Probably because of my experimenting with others, setup seemed not so bad. I like the ease of incorporating the descriptions, art etc and the innate feature of downloading these, relevant to the specific games/platforms.
Everyone has their favorite front end, and that's great. Use what works for you. Note that these other front ends probably have many, if not all the same features as LB/BB and are just as easy (or not) to setup. I just haven't taken the time to look back and see. Maybe I'll get bored and retry a few. Pretty much any front end can launch any emulator without side affects. Including any legit (current or past) version of MAME. Just may take some tweaking. (Srry to stray from the original Subject.)