- It acts like any true MAME frontend, no longer part of the binary, but a standalone app.
- Because it's no longer made to be part of MAME, it means it can be updated out of sync with it.
- It's programmed to use the Qt application development framework. Accordingly it can be (and has been) ported to other operating systems besides Windows. A M+GUI for Linux exists, bringing the look and feel of a MAMEUI-like frontend to the Linux (or even Macintosh) worlds.
- It's no longer tied to the aging, on-life-support MAMEUI code and is (from what I understand) a complete rewrite, but ending up with a user interface that "looks similar".
- It's still compatible with MAMEUI folders .ini format and whatnot.
- It supported a decent amount of MESS features before MESSUI was really a thing IIRC.