I was once a MAC guy, for many years, actually, but then, after a decade in academia, I naturally switched over to PC systems which supported and interfaced with all of the software I was using for my job. That stuck, and I have found that I prefer PC formats much better for my needs, professional and personal.
Windows user all the way. I'm a stickler for old habits, and I don't intend to swap to something new, unless it's so good that the world decides to move on to the new thing. But since OS is about as popular as Windows, I'm staying with what I love.
Also, Windows computers are cheaper and much better for gaming, so I see no reason to try out OS.