RE: Technology
I'm not sure what some people mean by using the word technology. As far as radio units, XM has been ahead for a while, but I feel with the 4g units that sirius came out with this year, the gap is either completely closed or so small to not make a difference.
It should be noted that Sirius and XM use different types of sat orbits. XM utilizes 3 (used to be 2) geostationary sats above mexico. The angle to the sats is roughly 40 degrees...and each sat is circling the earth in the same direction of rotation at a speed advance enough of the earth's surface rotation to stay in the same place above earth at all times. Very similar to sat tv, where you point a dish at one place in the sky and it stays pointed there forever.
Sirius uses (and forgive me if this term isn't exactly correct) a more geo-synchronous orbit...where the sats move, but they move around the earth, but follow the same time path every day. The following gives you an idea of what I mean:
http://www.heavens-above.com/orbitdisplay.asp?satid=26390
http://www.heavens-above.com/orbitdisplay.asp?satid=26483
http://www.heavens-above.com/orbitdisplay.asp?satid=26626
The sirius sats move from south to north, but by the time they reach the poles, the earth has rotated enough so that when the sat starts going down the other side of the earth, we've caught up with it. There are three of these sats operating like this, and the idea is that at any given moment your sirius receiver can find 2 of these sats...
In addition, the orbits of sirius sats are aparently higher than that of XM sats...so the angle of inclination is closer to 60 degrees. The idea here, is that you can look more 'straight up' into the sky to get the sat...buildings and trees become less of an issue. The result is that Sirius has been able to get away with far less repeaters than XM. XM has (when last I looked) something like 10-20X the amount of repeaters that Sirius had.
Now, in theory, Sirius' technology seems to be a better fit for cars/rural america/etc. However, I was convinced that XM's way was better...given that I could get XM signal better than my original starmate. That is, until I took note of how much of my XM signal was technically 'terestrial' and not sat. With the sirius unit, even though there are repeaters here on the Island....there are far less of them than XM.
In short, I think the older sirius equipment is problematic...which leads to the dropouts. Get a new unit (hell, they're almost giving away the Stratus and the InV. All you have to do is call them and bitch about the reception and they'll send you one for just the cost of shipping it to you...
RE: Programming
This is a philosophical issue...and I hope with the upcoming merger, that the two brand identities of Sirius and SM stay seperate...and that they approach programming they way each one does, independently.
Having listened to both, I can say with fair certainty, that XM's aproach is to dig a little under the surface and stay away from the big hits of the bands they're playing. Sirius aproaches it with more of a hit-oriented philosophy. On XM, you would hear alot more album tracks and sirius more released singles. This depends on what type of listener you are. If you want from your sat radio, to be surprised with under-the-surface, slightly (or tremendously) obscure tracks...then XM is the radio for you. If you want to listen to Sat radio to get a more familiar feel, then Sirius is for you. Personally, I listen to mostly BuzzSaw and Hair Nation, I'm not looking to get surprised...I want a station that's going to make me feel like I'm listening to the fm radio in 1985 (in buzzsaw's case) or 1989 (in hair nation's case).
XM, in the case of boneyard, was too off-putting. First off, they advertise it as a 'hard rock from the 80s' station. But you will frequently hear BuckCherry, Black Label Society, Pantera and Rush(!?!?) mixed in with the Slaughter, Van Halen, Warant, etc. I found it unsettling to be listning to Slaughter or Def Leppard...only to get hit in the side of the head with Pantera. It really sounded to me that Boneyard was confusing itself with two different stations...and the identities of the stations were simply conflicting. Some guys like that 'out-of-left-field' feeling...which is cool...I didnt. It only made me want to change the station. I felt the same way with Big Tracks. You could hear some cool AOR stuff on that station, only to be donkey punched with bad Genesis (i.e. I can't Dance)....It was unsettling.
I also like the fact that Sirius actually hires some DJs to create a station feel. XM only recently brought on their program directo, Kevin Kash....who only DJ's some of the time. Most of the time, it's obvious that someone simply thrust a handful of tracks (all without uniform tags, some upper case, some all lower case, etc) into a playlist and let it go. Maybe on Sirius, they're running out of an automated playlist...but they're making an excellent effort to prevent that from being aparent. It makes is more worthy of my $12 a month.