You can buy a unit at lots of places including big electronics stores. That is the easy part. Deciding which unit to buy can be difficult.
Big differences: Sirius has Stern, the NFL, March Madness, and NASCAR strating next year or the year after... whenever XM's contract expires.
XM has the MLB and Opie and Anthony and the Playboy channel ( I think ).
They cost the same for service ( or VERY CLOSE ) and you can listen to both on the web. And you can buy adapters to hook up to your home stereo. This is called a docking station.
I have had both services. They are both good. I switched to Sirius because of the NFL package. Music is "SIMILAR" on either service. But XM does have a more relaxed playlist, meaning a few less repeats. But I don't hear many repeats on Sirius anyway. So I don't care about that.
XM has a lot more subscribers than Sirius, and has been around longer by about a year or so. However, I have read NUMEROUS articles that say that Sirius is gaining customers at a faster rate than XM.... mostly due to Stern, the NFL, and the fact that XM will be dropping NASCAR, with Sirius picking it up.
In all honesty, I like Sirius better but both are good. It just depends on your needs. Oh, and do NOT expect "CD quality" sound on all channels. Both services alot different amounts of bandwidth to different channels as they see fit. Lower bandwidth means less quality.
EDIT: XM has a fully portable unit that you can take anywhere. Sirius has a hybrid model that seems portable but needs to be docked. But what that unit DOES have is the ability to record shows to the unit on a memory card for playback when docked. I am not fully sure of how XM's portable unit works, but is DOES NOT need to be docked.
Well, the Sirius unit is due any day now, truth be told.
