They’re totally different things. Pandora is really great for recommending songs based on similar artists, and Spotify is a lot more of an iTunes alternative, with a giant streaming library of songs.
Let me put it this way. If I wanted to listen to the new Shins album, I’d look it up on Spotify and listen to the entire thing. If I wanted to listen to bands similar to The Shins, I’d boot up a Shins station on Pandora.
I have a policy of never using apps that you have to access through Facebook so I haven’t tried Spotify. I love Pandora and listen to it through my tv.
I started with Pandora many years ago [10 or so?] and liked its ability to branch out from seed songs while still maintaining an awareness of type of music chosen. I don’t know Spotify
You don’t have to link Spotify to your Facebook account. Mine’s not linked. I prefer Spotify over Pandora because I can choose exactly what I listen to, but Pandora is nice when I want to listen to something new. If I can’t find something on Spotify, sometimes I can find it on Grooveshark.