Both are good and have there advantages. I love Slacker's large selection of pre-programmed channels in all music genres. Pandora's pre-programmed channels aren't as good. But I love the fact that everything is totally free on Pandora. You can create new stations, share stations all for free and on Slacker you have to pay to do those things. I use both, but I am a "free user" on Slacker and use that for their pre-programmed channels, and I use Pandora to listen to stations others created, like the Lucy channel on another thread about Pandora (thanks for that link, BTW!) But the best thing about both services is NO CENSORHIP AT ALL!