Kind of off topic, but perhaps interesting to those interested in either service...
The FCC mandated that both Sirius and XM need to work out compatible hardware specifications so that users can switch to either service using the same deck. However, there is no time-limit to enforce the mandate, so neither company has worked hard to make this requirement happen.
So in short, if you heard about future devices being able to run both services, well... keep dreaming.
USA Today has an article about it.
LINK