It is possible that there could be differences in the sound quality of the two. Consider that they are both different companies using different technology to do the same thing.
One thing that I have always wondered is how much digital compression do the two companies do to the audio? The audio data has got to be compressed (like mp3's are) in order for them to stream so much through the satelite, I just wonder how much. I wonder if it would be equivalent to a 128kbit, 160, 192 mp3, or higher?
