I've given this speil on other sites but: Apple Music is the only truly great music streamer out there.
For starters, it's all about music. You know, the thing you want it for? There is no podcasts, no audio books, no other forms of media trying to shoehorn themselves in. You open Apple Music to listen to music.
Second, the sound quality. Apple Music supports up to 24/196 lossless via ALAC, as well as lower quality settings on a per-signal basis, so you could set to stream in lossy via cellular and hi res on WiFi. On top of that, Dolby Atmos and "Dolby Audio" (all older 7.1/5.1/quad formats) are available on an ever growing library of albums, from the entire Talking Heads catalogue, to Yoshimi Battles The Pink Robots, to a considerable chunk of Pink Floyd albums. I'd argue that the surround stuff really shines on an actual surround setup, but the "Spatial Audio" implementation on headphones is solid (and works on all headphones if you flip Atmos to "always on")
Third; complete control over your library. Here's a great example:
On Friday, the jam band Phish put out a brand new album. One track was exclusive to vinyl. I made a recording of the track off my own copy of vinyl, edited the metadata of the version streaming off of Apple Music and added the track in the position it is on the vinyl version of the album. Now I have every track for the album on all devices, as local files are uploaded to the cloud. If I downloaded something off of Bandcamp that's not on streaming… adding it to the desktop Apple Music app will make it streaming on all devices via cloud.
Fourth; Apple Music is human driven. All the playlists are curated and ordered by human hands. Classic and new albums have extensive liner notes. There's a 24/7 radio setup with 3 channels being DJ'd by humans, and frequently known artists (Elton John, Estelle, Dolly Parton, etc). There are pages that show you stuff based on your algorithmic listening habits but more often than not, you're getting recommendations from other people… not a faceless algorithm.
It is admittedly not perfect. There is an infrequent issue where someone changes metadata on a release and it splits to component tracks in your library. The Windows desktop app is rough (and I've heard the Mac one is not much better), but relatively solid for me on Windows 11. Updates are tied to major iOS updates… but Apple does seem committed to working on constantly improving the service. Apple Music Classical, a side service included with your subscription seems like a glimpse of the future where you can see every performance of a certain piece, track a musicians career across all albums (not necessarily their own) and more.