I discontinued my Spotify service about 18 months ago because I went through the process of deleting my Facebook account, and the backend Spotify account was linked to it.
It turned into a pretty unexpected ordeal, I had to call Spotify customer service, they asked me if I could reactivate my Facebook account just for this, have them "fix" it, then deactivate again, etc. At the time Spotify Linux support wasn't very good either (don't know about now).
Anyway, I switched to Amazon Prime Music because I was already a Prime customer and figured that paying nothing beyond the Prime subscription was perhaps better than paying $8 or whatever Spotify's rate was then.
I am really glad that I did it. Amazon Prime Music has consistently worked extremely well for me on iPhone and iPad and in browser. With standard AT&T 4G service, even here in rural Indiana, I have no trouble streaming from Amazon when I go running.
The major downside is that their music catalog is not as comprehensive as Spotify. But I've found that there are only a handful of artists that I really love which I can't listen to yet on Amazon (Beirut being the one that I really miss).
The catalog is very large though. They have any type of music you're looking for, from country-western to African to the latest and greatest unheard-of indie artist. They just don't have exhaustive coverage of all of them.
If you are an extreme audiophile type and you really need to have completely exhaustive coverage of every possible artist, then Amazon won't work for you. But if you try out Amazon and find that it mostly covers the artists you enjoy and you don't really need the exhaustive coverage, and you happen to subscribe to Prime, then it's a great option.
Full disclaimer: I am not a fan of Amazon in general, but I am a fan of good products, and for casual music streaming from most, but not all, artists, I think Amazon is probably the best service available right now.
The way I break it down:
Spotify --> You require on-demand access to absolutely every imaginable artist, you enjoy heavy integration with social media clients.
Apple --> You may want to purchase the music, house it in iTunes, and own fully offline copies (not just caching, which other services can do too).
Amazon --> You're more casual about it than either of the above cases and you already have Prime. You either mostly listen to Top 40 stuff, or else for the less common stuff, you verify ahead of time that Amazon offers a catalog in that area that's good enough for you. You probably don't care about owning the music, but you still can purchase it via Amazon if you want to.