Since more and more cores are on-par with their standalone counterparts, im interested in using a Libretro core for my MAME stuff. I have a “somewhat” up-to-date ROMset (0.180) and no idea what MAME core actually corresponds to what ROMset.
With the ungodly amounts of MAME Roms and the plethora of different MAME cores, trial and error seems pretty tedious. Is there some kind of documentation floating around, shedding some light on each specific MAME core and its purpose ?
This site ^^ has a lot of information on different cores. In short, you probably want the core without any year after it. That one’s up-to-date with the official MAME releases. MAME2003 is the next most popular and it’s based on MAME 0.078 with support for some games from later releases backported in. MAME2010 is based on MAME 0.139, MAME2000 is based on 0.037b5, MAME2014 is v0.159-ish, I think…?
Thanks for the amazing answer !
I looked at the docs site before, but only found infos about the 2003 core.
But you pretty much told me everything i needed to know 
Again, thanks a bunch !
On Android, MAME, MAME2010 do not work. 2014 works great, and 2016 is OK
If you load any of the mame cores, it now tells you in the main UI down the bottom left which version of mame it equals.
I love Retro Arch, but MAME is not quite there yet for me unless we are talking about Android. Even on Android the actual and completely free with no ad version of MAME4Droid is pretty incredible and very intuitive to use. I still use stand alone MAME on PC because it’s way easier to navigate and runs just about anything I need it to. The only MAME core for Retro Arch on Android that I have any success with is 2014. I don’t even bother with the rest of the cores anymore.
Im looking into switching to Retroarch MAME for a rather silly reason ^^ Im using the Launch Box frontend and a PS4 controller. And since InputMapper started to have issues, im launching LB over Steam to take advantage of Steams controller mapping. Issue being: Steam launching LaunchBox launching MAME results in a black screen for whatever reason.
So, to cut down on relaunches, a Libretro Core is a much more comfortable solution at the moment. And so far, the MAME Core runs everything i usually play pretty well ^^
In my experience the problem with using the mame git core (without year) is that: if you maintain the core updated, you have to maintain the romset updated, which is time consuming, and most of the time you’ll not encounter differences, but some games will break if you don’t update the romset (killer instinct was last drop for me), so i stick with mame 2014, i added some extra files in the roms to have compatibility with 2016 core, but still not changed, i will if i encounter problems with a rom that are fixed in the newer one. But remember as the emulator progresses is getting more accurate but harder to run, meaning that if you are on the borderline for a rom, updating will eventually make the game unplayable in your machine.
I cut my arcade section down to 52 games (I had over 280 before; finally played through them and only kept the ones I really liked), so now I barely have to update my romset for each MAME update. I didn’t have to update anything going from 0.190 to 0.192 for example. That update was worth it for Akai Katana too 
I think the reports that MAME is always getting slower are overblown. I’m sure some drivers get slightly slower over time, but it’s never been enough for me to notice a difference in the years I’ve been using MAME on desktop PCs. Even on my old laptop or Athlon X2 powered desktop, only SH3 or STV based games had issues running stuff on the latest MAME. And recently, Haze got a recompiler working for CAVE SH3 games which made them run much faster.
In my experience, only keeping a hand full of ROMs can be a bigger hassle than keeping a ROMset up-to-date, if a ROM needs a file in a different ROM etc. Its a wild goose chase.
But i guess that’s the price to pay for an emulator compatible with tens of thousands of systems ^^
But yeah, im still waiting for the miracle that one day, MAME will have a simpler ROM system, with fixed ROMs per game. A man can dream