I got a new Murano after Xmas and it was pre-wired for either kind. We already have XM in a pick-up and Sirius in the 300C and they both have way too many channels to be able to listen to, so I guess it's just a matter of finding out if they include the ones you want. I think it's a wash with types of channels, actually. I HAVE found that the Sirius has less drop-outs than the XM, at least here in good old Michigan. I opted to get Sirius installed. Cost $400 and it didn't change anything on the dash with the existing Bose stereo.
Lots of luck!