XM and SIRIUS
I've both installed, XM in my Hyundai and SIRIUS in my CX-7.
1. Both will cutout in tunnels, in the city where tall buildings are prevalent, and under heavy tree canopy. Additionally, I've had cutouts on both services periodically on the open road. Not sure why that happens, it's irritating.
2. Channel selection on both are diverse. On SIRIUS, there are 7 - 8 channels dedicated to rock, alone, so I'm not sure where some posters seem to think there aren't enough channels to suit their needs. As for repeating songs, I've noticed that as well, but if that occurs I simply change channels. (shady) .
3. XM is NOT totally commercial free. Quote from their website: "as well as four music channels programmed by Clear Channel Communications carry a limited amount of commercials". SIRIUS is similar. I'm a bit disappointed that commercials have crept in, but considering that their subscriber base subscription fees aren't covering expenses, it's understandable. If I'm bothered by the commercials, I'll change channels.
Later, Vince.