Sound quality. I can't comment on Pandora because I've never used it, but satellite radio sound quality is far inferior to a CD.
Perhaps, but a car is probably the worse environment for listening to music for quality.
Pandora ONE claims to offer CD quality sound. That is their subscription service. I *do* subscribe, but I can’t tell you for sure whether it is actual CD quality. It was very good when I listened on headphones, but that was a few years ago now. Now we listen on PA speakers outside.