I was a long time user of Spotify and then moved to Apple Music when it launched. I resubscribed to Spotify recently as it’s supported by the (android based) head unit in my car (no car play or android auto support)
So, at the moment I have subscriptions to both and trying to decide which I prefer.
Spotify has a number of benefits: better performance, cleaner interface, better suggestions and auto playlists, lighter desktop app, easier integration with Sonos using the native app rather than the a Sonos one, integration with google home
Apple Music has a number of benefits: better integration with iOS and macOS, easier, more intuitive merging of purchased and streamed tracks, less restrictions (I can’t believe in 2017 that Spotify still has a 3 offline device limit and 10,000 song limit in your library). I also suspect it’s the only music service that will work with the home pod, at least initially.
Personally, I’m currently leaning towards Spotify because it gives a better UX for me on a day to day basis, but there’s little to choose between them IMO - they’re both good