Last I read Sirius has about 1/4 of the users of XM. The big things Sirius has going for it are NFL and Stern. Neither company has any kind of financial numbers that look good. There is a monthly charge for Sirius but I believe for some satellite televisions it comes free. I know they are also coming out with radios that can provide either service so the consumer will be able to choose from either one without having to buy additional equipment.
As far as clear channel I have always enjoyed:
http://www.clearchannelsucks.org/index.php