Apple Music's library features much more closely mirror the iTunes style, i.e. you have a library you can browse outside of just the "liked songs" pseudo-playlist. For instance, in Spotify (AFAICT) there's no way to browse all the songs in your library by artist; you can only list the artists you've followed, which is unrelated to whose songs you've liked, and go to their general artist page.
Personally, this is the top contender for a reason for me to switch away from Spotify.
Personally, this is the top contender for a reason for me to switch away from Spotify.