Financially neither company is making money. The last time I looked at the figurers (which has been awhile) XM's cost per customer was in the upper 80's while Sirius's was in the mid $110's. (meaning that each new customer cost the company X amount of money) XM has Sirius beat in the number of subcriptions. XM has 7.6 million subscribers, Sirius has 4.6 million subscribers.
I wonder how Sirius is going to be able to keep up the contract with Stern. $100,000,000 per year is a bunch no matter how you look at it. That's 1/2 a Billion dollars (yes with a B) in five years. Not to mention he does 4 days a week, and only 9 months a year. (I want that contract)
The company's pretty much split the new car market. Sirius has Ford and Chrysler, XM has GM, Honda and Toyota.
Sirius has one satellite in orbit, XM has two.
1 year chart Sirius Radio
1 year chart XM Radio
Neither has had a great year stock wise.
Personally I choose XM, because they have more to offer in the way of units that can do more, and they seem to be the leader in new product innovations. (the newest units have MP3 players built in and can record programing to play back when ever you want, up to 5 hours)
All of this could have changed since I looked into the different companies, I just felt that XM had the unit that I wanted and the programing that I liked. XM is going to be around the longest in my opinion, I didn't want to buy something and then have the company go out of business.