What.CD - not because of the free music but because of the community, recommendations by friends and discovering new music on a daily basis.
Right now I’m just listening to the “For You” section of Apple Music and very rarely discover something new. I also don’t really have a way to keep things that I like around as there’s no nice way to put things in your library if you don’t use iCloud Music library. Streaming services also miss a lot of editions or different recordings and their meta tags are usually very bad.