I <3 my Sirius. I how ever HATE the cheap ass fucking antenna's that keep breaking ever 6 months. I want to find an oem sharkfin from some car just to jack the antenna, because those seem to last.
Sirius and XM merged a while back. They should offer the same stations. I have only used XM and I prefer the old XM channels, so I say XM. Not to mention that XM sounds for fitting to a radio band type. FM, AM, XM
I've had Xm for 4-5 years and I'm pretty satisfied. Main thing i hate about it is the reception. It sucks in the rain and when your surrounded by trees. But then again, my antenna is located inside the car.