I have had XM since 03 and at one time was paying for 8 radios. When Sirius took over and killed XM, Fired most all the program directors, killed most of the great channels or combined them into the Sirius "FM" style of repetitive shallow playlists, I canceled 5 subs.
I have always had an XM aftermarket radio in my rides and still have factory OEM in my GMC Acadia. My wife had a P/T with factory Sirius but I never drove it much to know the difference, until we traded for the jeep.
The first thing I noticed with listening to my same favorite channel in the jeep is it sounds like shit, like coming out of a tin can. Much worse than the same channel on my XM radios.
I have spent years on the XM forums so I know the XM vs Sirius war, coke vs Pepsi, Jeep vs -------.
Bottom line is XM was way ahead with better codec, tech, radios, Sat's etc etc. But the battle of programing and trying to outdo each other with more channels took more and more bandwidth, causing more loss of bit rate per channel and sound quality. Just listen to a talk channel, talk about a tin can.
Back in the "Day", they were near CD quality.
Now that they are merged as one company, the fact remains that they are still 2 different systems. XM radios will not receive and decode the signals from a Sirius Sat's and vice versa.
There are some channels that still sound great like Deep Tracks (XM side) and a few others running higher bit rate. But i am disappointed at the sound quality of Sirius in the jeep and thinking of installing my XM Pioneer Inno even though its nicer to have sat radio integrated in the factory head unit.
Nov 12th 2008, the day XM was murdered by Sirius.