Spotify and Rdio Mac apps

Hey guys,

A little help needed here. I'm looking at getting a 2012 Mac when they're announced. With that, I'm also looking at buying either Rdio or Spotify.

Could anyone tell me: what are the good things about these apps, and are there any disadvantages to using this? This especially applies to Rdio, as they also have a web-app, which Spotify (annoyingly) doesn't.

So yeah. Jst need recommendations and your thoughts about these two apps.

Thanks a lot!