Worship The Glitch notes that Spotify is on the iOS top free apps while Rdio is on the top grossing apps in the music category.
You can’t use Spotify or Rdio on mobile without paying.
This suggests that iOs users download Spotify, but actually use Rdio.
No. Rdio allows in-app purchases for subscriptions. Spotify doesn’t have in-app purchases for subscriptions. The result is that Rdio grosses more for the App Store than Spotify does.