just to note with spotify: they have a singular goal/drive to keep and grow their userbase every quarter to offset their costs and to stay 10 steps ahead of Apple Music. So if you want a music service that has constant updates and feature changes, it's with Spotify.
Youtube Music is at the moment a nice extension for people who already use the website as their music service without having to pull down 720p on their data plans for each song or their workplace's network bandwidth. and if you know what you like and what to look for, it's very serviceable. It's very similar to Amazon Music where it's pretty plain.
But for my use-case it's great for my workflow where I can queue up an album or even a music video next and watch it and then change my tab to something else while listening to music.