I have had Sirius for about 3 years now and I hate driving any car without it. As far as Sirius or XM, it all comes down to personal preference with the programming. Basically each has commercial free music, but I chose Sirius because of the NFL coverage, Howard Stern, and others. They both run about $12.95 per month, or around $11.50 if you pay annually. I would assume that Sirius would be easier to install on your car becasue BMW sells Sirius packages and not XM.

If you spend a lot of time in your car I would highly recommend it.

Pros-Many channels of commercial free music, news, talk radio, comedy, sports, traffic and weather that are available from coast to coast. You could literally drive from New York to California without having to change the channel.

Cons-you have to pay for it. That is honestly all I can think of.