I have 3 vehicles that have either Sirius or XM. What I do to save a little money is pay for one vehicle plus internet streaming. We use the app on our phones to bluetooth the audio through the stereo in the other 2 vehicles. It works fine as long as you have cell service and a data plan to cover it. The data useage is no more than Pandora. I use it because I can't get sports or news on Pandora.
If I recall correctly, there are some stations you can only get using internet streaming, so it may be worth your while if you like specialized stuff.