Last FM vs. Pandora.

Recently I have been impressed everyday by Last FM and their range and quality of songs (especially underground hiphop). I've been a loyal Pandora listener for years, but sometimes it seems more like I'm listening to the same 50-song-shuffle, not an infinite world of killer tracks. I spend tons of time in my studio with music bumping, so I was very pleased to find another more versatile internet music shuffle.