If you enter video-related enthusiast scenes, such as fansubbed anime releases, mpv is recommended over anything else across the board. There are releases that break in VLC, and mpv is usually first to support new features. It also has particularly good defaults in terms of good and accurate playback, so where you might see some people say "install mpc-hc and these scripts and change these settings", with mpv it's just "use mpv". mpv
is extremely configurable on top of great defaults also. Setting default audio and sub languages in order of your preference (such as enm before eng and en if you prefer honorifics tracks) is a common tweak.
I thought VLC was awesome while growing up, and at the time it probably was compared to Windows Media Player and such. I remember a common bit of praise was that it supported more types of video files. I haven't really run into anything mpv won't play (I even use it when an image I saved ends up as .html for some reason and then use the info screen to determine the real extension it should be so I can rename it), but also I'm guessing we've standardized more on codecs and containers these days which doesn't hurt.