XM has 12 channels with no commercials, rest have commercials but I don't think they are nearly as long as on the radio.
Sirius doesn't have any on their music channels, not so sure about talk (hate talk radio, main reason why I don't listen to normal radio - because those stupid ****s talk in the morning), sports, or comedy channels. Actually, pretty certain none on the comedy.
Prices seem to have changed since I last looked, and they now offer plans for both of them. Check their websites for details.
The main selling point is that they don't have annoying bellybutton **** DJs talking all the time. Although, lately on Sirius, they seem to be spewing a little longer. Getting annoyed with it.
If it continues they will get a very angry letter from me containing copius amounts of fecal matter.
-SW