XM, Serius -- Quality Sound?

I'm looking to upgrade my car audio system -- curious about XM and Serius -- anyone know about the quality of the broadcast, the KBPS rate, etc? Does one sound better than the other? How does it compare to, say, an FM or AM signal? Thanks.
Can't commnet on XM, but I've had Sirius in my car since last March. (I'm pretty sure the sound of the two services is comparable, since the technology is similar, if not the same.) Sirius is great. You either get the signal - very clear, no static - or you don't. Drop outs are *very* infrequent, especially in larger urban areas, which are served by ground repeater stations. Regarding sound quality - far better than any AM I've ever heard - - and most, but not the best, FM.

In terms of choosing between the XM and Sirius, check out their websites and make your choice based on programming. (I chose Sirius because I listen mostly to jazz and classical, and I (slightly) preferrred what I heard when I compared the offerings of the two on-line.) At the time, XM had some commercials on its music channels and Sirius music channels were commercial-free, and this was also a factor in my decision. As of this week, however, XM has announced it too will offer commercial-free music channels.

Price-wise, Sirius is about $13/mo., while XM is only $10. Still, the price differential is insignificant, and you should make your choice based upon whose programming you prefer. Whichever service you select, I'm sure you'll love it!
Hey Rob, both are compressed audio formats so sonically they are not the "best" sound available. From my experience they are better sonically then FM and light years better then AM but not as good as CD. Both formats have there ups and downs if it were to come down to the two of them get the list of Channels they offer and get the one that has more catagories that interest you.
I have listened to XM in my son's Mazda Protege "listening room" and when simply listening casually, and with routine car background noise, better than AM by a mile, and as enjoyable as any FM in the car that I have heard. The immense variety of music choices avoids any chance of boredom, and there is a limit to how wrapped up in the audio experience one should get when driving. I did not hear any specific recording which I already knew, so there was no absolute reference comparison.
If you simply want to relax and enjoy while driving, there does not seem to be any major flaw.
The moderate cost auto sound system I listened through is not up to home stereo standards, so a "competition quality" auto system may yield a different impression.
I have used Sirius in my car for over a year now (I use the Kenwood FM Mod & controller). It is a good service, but so is XM. Look at the programming in order to make your decision (I think Sirius has more commercial free channels).

If you are upgrading and will utilize the FM Modulation option, you will not get ultra clear reception. It will be as clear as an average radio station broadcast. The best way to get clear sound is to upgrade the head unit to a satellite ready unit. I your car has stock BOSE speakers this may not be very economical (most head units will not match well with BOSE. Consult with a technician on this issue. Good luck!
Thanks for the info, guys. In this area, we don't get real good radio reception, but I have heard that XM and Serius come in much better.
I know I won't get CD quality sound, but if it is better than standard
FM and I can get better reception, maybe I have a chance at getting
some decent music through the car radio. I have pretty much given up listening to CD's in the cars -- way too much hassle and too many lost
and broken Cd's. You end up driving around with the same 6 CD's in the car for months. Alpine is coming out with a car stereo that will interface with an Apple i-pod. This is really appealing to me. With a 40Gig i-pod, I could burn a couple hundred Cd's with very little
compression and have some real selection at my fingertip! Anybody know how many CD's will fit in 40 Gigs UNCOMPRESSED? I'm betting it would sound a lot better than any kind of radio. At this point, there is no way I am going to get sound in my car like I have in my listening room and I am not even going to try to approximate it. For in depth listening sessions, I will listen at home to my reference system. In the car, I just want more variety and better sound than I am getting currently from crappy AM/FM reception. I stopped bringing CD's out to the car a year or so ago, but I would love to have a portion of my collection on a hard drive like the i-pod and plug it into a Head Unit
like the Alpine. Of course, I will audition the components to get the best sound reasonably available and I will also probably upgrade the speakers and such, maybe add an amplifier, but I am not going to go as deep into the car system as my home system. Really. I'm not. I swear. Really!