Opinions differ but, I prefer Sirius programming over XM.
I like good ol' Rock-n-Roll. Sirius has stations like Classic Vinyl, Classic Rewind, The Vault, BuzzSaw (newer classic rock), Hair Nation (all the 80's hair-metal bands)...plus the usual 70's, 80's, 90's stations. The 80's station plays really great 80's songs (if you're into that). If you are into the 80's stuff, you'll know just about every song. They have 4 of the 5 original MTV VJ's on as DJ's (JJ Jackson passed away several years ago) so, they're really good.
Sirius has Howard Stern (if you're into that) and Marta Stewart (if you swing that way), NASCar and NFL radio.
In contrast, XM has Major League Baseball, NHL, PGA tour, Oprah, and Sean Hannity
I've never found a decent "hard rock" station on XM. The 80's stations plays some really obscure stuff. I mean, they'll play a song from one of the many 80's one-hit-wonder bands but,....it's not the hit!! I mean, in my opinion, if you're going to play a song by A Flock of Seagulls, it needs to be "I Ran"...if you're going to play a song from A-ha, it needs to be "Take On Me". But, it's music so, opinions differ greatly...that's just mine.
As for hardware, I have the SC-C1 with the MJS interface. Could not be happier with it. stupid-easy installation and setup and works seamlessly with CentraFuse 1.47. The only minor surprise I had when I got it was that it requires a separate ground and +12V. I assumed that it would get power from the USB but, it doesn't. Maybe all of the other Satellite Radio interfaces require this too. Could be a current-draw issue that makes them unable to get power from the USB.
CentraFuse handles the Satellite Radio very well...with only a few minor glitches. 1.48 is supposed to resolve quite a few of them (the Satellite Radio plug-in doesn't seem to like Hibernation with Windows so, you can't use the Hibernate feature if you want the Satellite radio to work when it wakes up....I'm hoping this is resolved with 1.48) and, I've reported a minor issue with the song titles not always updating but, smeesman (the contact for the Satellite Radio plug-in) has found the software glitch and assures me that it's fixed in 1.48. But, let me be clear, it's a VERY minor deal.
I listen to Sirius every time I get in the car. I listen to it more than I listen to my mp3's.
Hope this helps.