XM Satellite Radio
XM satellite radio has the most subscribers (almost 9 million), and reviews say XM has a slight edge over Sirius when it comes to music sound quality and signal reliability.
Though Sirius has more professional sports programming and Howard Stern, XM has the exclusive rights to broadcast National Hockey League and Major League Baseball games. It also presents live concerts and original programming. XM’s schedule includes The Bob Edwards Show, Oprah & Friends and Theme Time Radio Hour with Bob Dylan. If you only want to listen online, XM has the edge, with a cheaper $8 per month web-only plan.