Well, certainly in the home recording world, you can figure finances probably have a pretty big impact on platform choice, and Wintel boxes have always been cheaper. (I bought my first PC in 1986 and, though I was amazed at what the Mac could do, I got an x86 simply because of price.) Today, there's no reason to choose a Mac for audio recording, since even the most basic PC has enough power for that kind of work and there are so many DAWs now that run on Windows.
But, even with a rough guestimate of a billion Windows PCs and 100 million Macs (numbers pulled out of the internet air last year), the breakdown of pure OS X DAWs is about 11%, so not a shabby showing, and shows a 23/77% split toward Logic, which doesn't surprise me. And, there might be a few folks running other DAWs on OS X, since, as you note, there's no platform breakdown.
Today GB is essentially a defeatured version of Logic Pro X and supports all the same 3rd party plugins. The UI enhancements would be the main reason for a home recorder to upgrade at this point.