Apple Music is privileged when it comes to Siri. I currently have both a Spotify and Apple Music subscription, and one of the main reasons I prefer Apple Music, aside from shuffle not playing the same 20 songs in a 2000 song playlist, is the great hands free functionality. I can add songs to playlist, play a song next instead of adding it to the end of the queue (which is more of Spotify STILL not having deque support), and I know there are other things I've run into Spotify can't do on Siri, but I'm blanking at the moment.