When YTM is better than GPM:
1/ Auto-created playlists, especially after you just search for a song and hit play. On GPM, it would play different covers on the same song (basically all the search results) by default, unless you started a radio, which is a cool concept but was hit and miss in practice. On YTM, it continues with similar songs, and I have liked their selection so far.
2/ The library seems to have increased; I guess they have access to more songs that were YT exclusive for some reason.
3/ While I normally never use video mode on YTM, but once in a while for a cool song, it's nice to be able to seamlessly switch to video and cast to my TV.
On the cons side, I don't like the playlist management and home screen UI (which is what I hated initially), but it's not bothering me much anymore now that I am getting used to it I guess.
Initially, I had planned to just cancel the subscription, but held on because using YouTube with ads was just plain intolerable. I get reminded of this everytime I open a Youtube link on my work account Chrome profile by mistake.