When traveling, I often like to listen to music. Unfortunately my choice of music tends to be classical. Classical music listeners are a minority, and most places have at best one classical station and that will be filled with commercials. One of the reasons I love XM Radio in my car is I get two good classical stations (a station that plays "popular" classical (e.g. movements of symphonies) and one that plays full-length pieces that may be more complex). At home I have Comcast's Music Choice that has two similar stations. Because I have accounts with both, I get access to their web sites.
Now that I'm out of the office (and have headphones) I've spent a lot of time listening to both. I've come to the conclusion that, content-wise, Comcast and XM are about the same. The pops channels play the same assortment of Brandenburg concertos and movements from Tchaikovsky dances and the full classical channels play everything from Shostakovich string quartets to Ives to composers I've never heard of. Both music streams are of similar audio quality, at least on the $10 earphones I'm wearing (my Sennheiser headphones might show more difference but they're bulky to pack).
But I'm listening more to XM. Why? User interface. XM feels lighter-weight and puts my favorite channels at the fore. With Music Choice, it's many more mouse clicks to get to the UI where I tell it to switch to one of the two stations I want to listen to.
In any event, both Music Choice and XM are incomparably better than the local classical stations, sadly, especially since they have no commercials.