I opted for the XM since it uses my head units display. I didn't want to have some external extra stuff cluttering up my dash. I have enough extra c!#p there as it is. XM just anounced that they are going to raise their prices in april, but they are offering more stuff than they do now. You can get the new feature subscriptions for the old price until that time.
Now if pioneer would only come out with a removable solid state hard drive like Music Keg, or Neo Jukebox. I'd be stylin.