It all depends on what you want from your OS:-
If you want a fast,secure,browsing experience for research etc, then I would say LINUX wins every time, If you want a great PC based gaming platform then M$ has that one licked!!
If you like eye candy and audio pleasentries- then again M$ is on top, However if you like the thought of developing softwares within a community for the mutual benefit of thousands of greatfull users for FREE, then LINUX triumphs again.
There's so many PROS and CONS for each OS that it may just be a case of reviewing each one till you find your comfort zone.
But being that M$ has a much MUCH larger advertising base, most people just settle for Windows without looking into other OS that may possibly suit their needs better.
I use both and they both get used for different purposes but as far as my hardwares/softwares/customers are concerned- M$ seems to get the most use, but I'm sure that if M$ was FREE to use , then this thread(and many others) would not be happening.
End of the day- M$ programmers are mostly paid for what they do after college/university courses etc and rely on the money they recieve for their efforts where as LINUX is mainly volunteer based and is a MAJOR reason for the OS's (distros) being FREE(apart from a few wider,concentrated developments)