Spotify vs. Deezer: User interface and functionality
Spotify vs. Deezer: Music discovery
Both Spotify and Deezer create Radios or Mixes of related songs based on songs and artists. Spotify also creates them for playlists that you make. All in all, the discovery features of Spotify vs. Deezer are very similar.
Winner: draw
Spotify vs. Deezer: Content and availability
Winner: Spotify
Spotify vs. Deezer: Audio quality
Winner: Deezer