I've been trialing a few Music Streaming Apps for my Lumia 950. So far I've tried:
Spotify and find it good but lacks functions that are put into Android and iOS and that annoys me.
I've also used Groove and like the clean UI for it and it's had all my tracks. But I like curated playlists and suggestions made on my saved/liked tracks. I like this because it helps me find new music or tracks I've not heard of. Sadly Groove falls down in this area. If they add this in or improve it then Groove will be very good.
I am currently using Deezer and I am really liking it. It has some great playlists, it's Flow function mixes my liked tracks with new suggestions. The UI is quite nice for a Windows Phone app.
The problem I have with music streaming in W10M is that the Win OS seems to mess up the app functions as well as the lack of decent app controls on the lock screen. iOS defiantly has the lead in music streaming apps.
I'm now looking for some other streaming apps to trial once my 30 day Deezer Premium runs out.