I disagree... They each have their strengths.....
Sirius has NFl, XM has baseball. Sirius has NASCAR, XM has IRL. XM has Opie and Anthony, Sirius has Howard. Sirius has Playboy and Maxim.... OK, they win on that one....
But XM has Cinemagic (Movie Soundtracks) and UPop (Pop from around the world). I like both of those genres.
I have both services and both are worth the money to me. I wish there was a receiver that could get both, but I have a Sky Fi2 hard wired into my car, and A Sirius One receiver that I take from car to car... A jumble of wires, but it is pretty portable. The unit's FM signal is really weak, and here in the NYC market where there is a frequency in use at every spot of the dial, it can be a nuisance.
The only issue XM is mixed up in is a lawsuit where record companies are suing over the ability of the XM radios to store music, which Sirius radios can also do if I am not mistaken. If they win this lawsuit, do they go after Sirius next?
I think they will eventually settle by kicking back some greenbacks to make it go away. We'll see...