I moved to YouTube Music from Spotify and I really miss being able to move the songs around in a playlist on the mobile app. I used to spend a lot of time curating playlists where order mattered (I might avoid having two songs back to back that are the same tempo/vibe, or I might tell a story with the progression of songs in the playlist).

I'm also annoyed by the fact that sometimes YouTube Music will hang forever on a blank loading screen instead of accepting that there's no connection and sending me to my downloaded songs. I don't know if Spotify does better about this because I never had Spotify Premium.

However, one good thing about YouTube Music is that you can find covers and unofficially released songs much more easily. I search for covers often, to see how others might interpret a song I like.