YouTube's music library feels richer than Spotify. A few years ago I was contemplating a switch from YT Music to Spotify (I like Spotify's UX), but a lot of stuff I enjoy listening to was missing. But I might just have a weird taste in music.
Yt music also supports tapping the side of the screen to jump forwards or backwards in 10 second increments. Seems like a trivial feature, but holy shit I have needed it my entire life. The ability to both rapidly and finely adjust the time is huge when listing to things like live shows that are a 2 hour video.
Crazy but I don't think I have ever had a program or hardware player that could do both. Always either fast forward/rewind or trying to finely slide a slider.