Interesting, although perhaps also just a reflection of the relative market saturation of each platforms.
I get the distinct impression this is more about how businesses and other large organisations handle patching. I can totally understand the mentality around finding a stable configuration and sticking with it but you also need to be putting int he work to keep moving forward, at least as far as the security patches go.
I wonder if MS had anything to do with the message being it was XP machines that were the problem, I mean they really want to be able to forget about the XP platform. This was initially perfect from their point of view and would have remained so until it hit the NHS at which point not fixing the problem in XP became extremely bad PR.