I used both over the year and there are still things that are really annoying in mpv:
- you can't render on a Chromecast
- opening a file that does not work does nothing, you don't know what's happening, is the file corrupted, is the codec not supported ??
- the no ui idea is nice for opening a single file, but then you go to the rabbithole of millions of settings / config to do anything more complicated, playlists? ( why can't I drag and drop on the window )
- it's hard to compile, so it's up to you to find up to date version on your distro