I preferred GPM in every way except that it would silently remove songs from my playlists, probably as a result of the publisher updating or removing them. This lead to me losing songs I had painstakingly worked to discover over many years. I discovered this only after several years of using GPM. Spotify seems to leave removed songs in playlists but disabled, which at least means I don't forget them.

The Spotify UI is atrocious. It must be designed for income/royalty maximisation because it certainly isn't designed to help me find and play the music I like.