I prefer XM for a lot of reasons, one of which is their superior technology. However, if I can't get NHL on XM then it's going to have to be Sirius.
I was a DishNetwork customer for years while they were promising NHL CenterICE. I got tired of waiting and missing games, so I switched to DirecTV and have had it ever since.
The investment in either is relatively small, $100-$200 initially and then the monthly fee. If I have to live with Sirius for an undetermined amount of time, until if/when XM offers NHL boradcasts so be it. I'm not out a large investment and in the mean time I can listen to the games.
Apparently neither offers MC racing so that's what it comes down to for me.