XM vs. Sirius

My wife's birthday is next month and I've decided to get her either an XM ready or Sirius ready head unit for her Nissan Xterra. Which one should I choose? Sounds like both have a loyal following. I welcome any input you guys have.

Anybody have an opinion on either of this 2 options? I was planning to buy her either an XM ready head unit or a Sirius ready head unit.

I think the two services are comparable, just go with whichever one just get the head unit you like the best. I'd sugges Alpine or Eclipse.

if im not mistaken all satellite radio is the same. its kinda like choosing cable companies ot internet service providers. they all take you to the same place. only differences are price and receiver. but if you have a h/u that is xm ready. then price will probably be the only difference.
i think, i dont have too much experience with satellite radio. just what ive heard.

sirius is more geared tpward sports and live entertainment stuff, XM is more plain music stuff