I'm damn near 100% opposite of Saf-t. I have XM in my truck, but the rental car I spent a week in had Sirius.
The music selection was far more limited on Sirius, as well as plenty of commercials on both.
Sirius seemed to have TONS more sports stuff, though none of it interests me on either.
It only took 6 presets to get all the music channels I cared to listen to on Sirius, I've got 11 used on XM for music.
I've heard Saf-t say on more than one occasion that the music repeats heavily on XM, that you could set your watch by it, etc.. When is the last time you had XM? I don't find that to be the case at all. Maybe the programming has changed.