Benefits:
DirectX 9 support, so older PCs can handle 1.1 content with better driver and hardware support (it's more widely supported than OpenGL 2.0 on Windows).
Built on top of Allegro 5, so any platform it supports we can too, like Linux, macOS, Android (I kinda like how this was the library the first versions of M.U.G.E.N used too).
Exploit all stuff we get for free from Allegro 5, like video playback, audio codecs, ...
An original M.U.G.E.N like experience (even the log output is pretty much the same).
Additions:
Zip & 7z support, and archives can be used everywhere if they internally preserve the standard folder structure, as if its contents where outside the file in the same folder (except mugen.cfg that must be writable).
OGV videos (Vorbis audio & Theora video) can be used everywhere a storyboard is supported. Replace storyboard.def by video.ogv.
Bit shift operators >> and << where implemented.
Animation support for big portraits (maybe small ones too later). You can specify anim for these on M.U.G.E.N but it's hardcoded as spr 9000,1 anyway (ignored, but now no more).
Pre-caching works with hardware acceleration (on M.U.G.E.N 1.1 this works only in software rendering mode).
Content redirection. You can specify a subfolder to search for content, otherwise it uses the executable root directory like M.U.G.E.N.
SafeMode = 2. The same graphic result as SafeMode = 0, but runs on older hardware without render to texture support, like SafeMode = 1.