I have both so let me offer a little insight. Remember that YMMV as I can only speak to my personal experiences & uses for AM (my personal acct) & Spotify (reimbursed & used for work). Both have things I like and things I don't like. But the reason I initially moved from Spotify to AM years ago was because of the Apple Watch integration. And that Spotify bought & killed a 3rd party app that allowed downloads to the Watch. It left a really bad taste in my mouth that they would do that. So I left and moved to AM.
Apple Music obviously has great integration with Apple products across the board and works much better with Siri. The Siri part really only matters, to me, when using CarPlay or when I'm using it on my ATV. It has integrated easily w/ my Sonos speakers and works fine with Alexa once configured correctly. And as stated above, Watch integration was key for me. The playlists have gotten better over the years and I really like the Friends playlist. As for selection, this has also improved for the things I listen to over the years. I've seen other complain about the lack of Classical music. Others have complained about Jazz as well but haven't seen anything missing that wasn't also missing from Spotify.
But I really hate the AM interface on Mac, on iPhone on iPad. It's really bad. Why is everything stark white and all the icons so large??? Why is it so hard to figure out which playlists are downloaded? If you go to the Downloaded section, even if there is only 1 songs that overlaps in another playlist, it'll show that playlist with that singular song! Why???
It isn't intuitive to find things or for discovery. There are actually TONS of playlists but you have to have intention to find them. The radio stations are good. And the music shows are a nice throwback to actual radio but I don't find I listen to them often. I really recommend it for people who know what they want to listen to and like to build their own playlists. It takes little time to train their algorithm but it's in a good place for me and they are building more
playlists.
I kept my free Spotify account and used Houdini or SongShift to move playlists over and it worked pretty well. I no longer use personal MP3s to upload to the iCloud library. That got messy but I have them backed up on a drive just in case. I've not found a need to go back to those. I do have a couple of dozen not-on-any-streaming-platform albums that I loaded up after the initial debacle but wow what a mess that was. I'm not an audiophile so sound quality is fine for me.
Best if used on your own Apple devices only. The windows app sucks but they do have an online site now
https://music.apple.com/login
Spotify. If only they had played nice with Watch in the earlier years, I probably never would have left. But that's fixed now and works well. Better than AM, actually. I really like the way music, podcasts and syncing to the watch are all inside the app. I'm so annoyed it took so long. lol. I Obviously their playlists for discovery are so much better, great for social sharing and seeing what your friends are listening to. There are also the Year-end playlists & metrics that are awesome but this is available on the free account as well.
The UI is much easier to navigate and more intuitive but it has been getting more and more cluttered over the years. I recommend the Premium account to people who want playlists made for them or have their own library they want to sync if they have lots of not-on-any-streaming-platform music. It's much easier to manage on Spotify than AM. Playlist & folder organization is MUCH better on Spotify. By a lot.
Spotify works great w/ Alexa and my Sonos speakers. Does not play well with Siri, as we all know. Great if you use mutiple non-personal Apple platforms.
ADVICE: Sign up for the
free Apple Music trial (there are a few ways to get this so do a search or if you have
Verizon). and use Houdini or SongShift to start building playlists and training the AM algorithm. Keep your Spotify Premium account for now but try to use AM more during the trial to see if you like it in all the different ways you use use. Look for the music you like, dig into the Radio & playlists. It takes time to switch and get used to something new! Set a reminder about 2 weeks before the trial is up and decide if you want to keep.