(Your parents bought you a car but you can't get a job?)
If you get XM or Sirius it won't matter in the (near?) future. The two are merging and just paid the FCC some money for some violations so they could carry out the deal sooner.
Personally I own XM and I love it. I bought it back in 2005 with my christmas money and have been addicted to it ever since. With XM you also get an online version (I think Sirius has an online too?) There is always a raging debate between which is better sirius or xm, there are a multitude of Dual-Subbers (people who own both) who give side by side comparisons. From the information they provide I assess that XM has a deeper playlist beneficial to the music I listen too. However, I don't know about the depth of the playlists for your genre on either service, but I know for multiple genres XM holds the better playlist.
As for sports programming? Thats the reason I went with XM, but I'm a baseball person. And college football(basketball too)
To me personally I find satellite radio to be worth every penny I pay for it, and as a high school student and college student paying for it was rather difficult at times, but I made it work. However I am an audiophile (with the tattoos to prove it) and enjoy the opportunities that satellite radio provides me to discover new artists that might never make it to terrestrial 'mainstream' radio.