To me, Bandsintown is the killer app for music tastes in the cloud. But Deezer doesn’t have Bandsintown integration because the Deezer API does not allow Bandsintown to get the information it needs to update your music profiles for them.
I’m not necessarily going to switch to Spotify because I just don’t like supporting monopolies, but at the least the lack of Bandsintown integration makes me reluctant to use Deezer as much because there is not that gamification incentive to keep adding to my favorites and playlists in order to get that picked up by Bandsintown.
In short, the lack of Bandsintown integration allowed by the Deezer API makes me reluctant to do any extra looking for new music and therefore to use Deezer more. Spotify has it, so it’s technically possible.