While they're technically the same type of software, it's still sort of like comparing apples to oranges.

VLC is your kitchen skink media players that comes bundled with basically everything possible.

mpv is more of a minimalist media player that let's the user add the features themselves using add-ons.

Me personally prefer mpv since it's minimal in every regard. I have turned of the OSC, and I use the keyboard for everything. I don't use a lot of extras, but the ones I have, is add-ons I couldn't probably live without, like yt-dlp and SponsorBlock (for YouTube).

I even use mpv as my music player with playlist that I manage using Neovim and the tool echo (to add new tracks to my playlists).