I've used both apps for an extended period. Personally, I liked Rdio slightly more, I just feel it looks (I prefer the lighter background) and handles better. I also think their recommendations when I'm listening to their radio are a better. However, I haven't really looked into too many apps on Spotify, so they might have one that does this even better. On the whole though, both services are extremely similar so if you like Spotify a lot, theres probably not much point to switching