XM or Sirius?

[MysticBlueX3]

I am currently driving a rental that has XM radio. I know, a rental w/ XM? WTF? Well I ain't complaining. I got to play with it on my commute to work and I must say, XM is great! You can browse through each station by catagory which makes it very easy to find stations you like out of the 250+ stationas. You also get artist and song information which most radio stations don't offer. I know BMW only offers Sirius but I'm pretty sure it functions basically like XM. Can anyone comment. Is navigating through stations pretty simple with the BMW controls? The rental had a couple extra buttons just for XM. I'm saving up for a Pioneer AVIC N2 navaigation which supports XM and XMtraffic. Anyone used XMtraffic?