I'm relatively new to what I'd call "strict" Mac OS use.
Back in mid-2000's, I picked up a used blue iMac on eBay just to play around on. Didn't get too much use out of it, mostly because my Windows laptop was a bit better at the time (not hard to believe on a 4-5 year iMac). I stayed with Windows through college, mostly due to lack of finances to buy a Macbook.
After college, I bought an Intel Core2Duo iMac and that became my main desktop. It was about 5 years old, but it got lots of use for basic tasks and music composition software. It was about this time I also bought an Apple TV, which was seriously the best purchase of my life besides my car, haha.
Back at the beginning of November last year, after using a 4 year old Windows PC that had slowed down DRAMATICALLY since I bought it in late 2011 (probs manufactured in late 2010), I bought a new-in-box late 2012 Mac Mini (6,1) from Best Buy shortly after the newest Mini was introduced. I decided this one was better than the 2014 refresh due to the lack of upgrade-ability. I instantly upgraded to Yosemite upon first boot.
To the point of the thread: each OS has its pros and cons, obviously. I love the simplicity and useability of the Mac OS, specifically OS X. Windows has a bit more expandability and utility, I think, as far as programs go. Mac OS has definitely bridged the gap to the point where there almost isn't one. However, Mac OS works MUCH better on older hardware than Windows does on older hardware. It truly all comes down to what types of features, programs, etc. a person wants and needs. I'd have to say that Mac OS is better overall, due mostly to security and the ecosystem being so well-developed for all of Apple's products. I now currently only use the Mini for my computer. I have an iPhone and, of course, the Apple TV. Still getting use out of my first gen iPad as well. I've basically cut out Windows from my life, even though I still have that laptop from college and it runs (not well, though). Waiting for the day I can afford a rMBP.