I personally prefer SIRIUS over XM. They got the OK to merge, so who knows what's going to happen. SIRIUS has a much better variety of music. The best way for you to find out which you like is to go to both of their websites and signup for the free online trial. The stream quality is low, but you can browse channels and get the idea. XM was too boring for me and the music wasn't very good.
I put SIRIUS' Sportster5 in my Cadillac and love it. I also have the home kit so I can just undock it and listen to it through my computer's sound system. The quality is good and SIRIUS also modifies the bass levels to provide a better quality of sound.
Hope you can decide and will like your selection.
