They are similar where they can taylor music to your taste. the interface of musicovery is definitely sexier than pandora, as you can see below. you can have a visual of any songs that are within your genre list selected on the left, and jump straight to the song of choice. from what I could tell, Pandora does not have that same option, however it does have another option that makes up for the lack of musicovery-like features in that you can input a “Radio station” which is the name of an artist or band that you like, and it automatically taylors the radio station to the music style that is very similar to that artist. I say that’s pretty slick.
You can sign it to both of these sites. Registration is free for the basic membership, and costs a pretty reasonable amount for the hi-def version, and a few more features available. To me, the free version has been working fine. Maybe it will for you as well. Give it a shot, and post which you prefer, and maybe even suggest some of your favorite sites for streaming music?