The myth persists about Macs being better for photo editing and graphics/creative work, and one time that was very true, back in the early-late 90s when Macs were 32-bit and Windows was just a 16-bit dog. Think 4 channel color, CMYK or RGB and transparency - no go on early versions of Windows, while Macs handled all this stuff. That's why the publishing industry all went Mac back in those days, and all those apps you use on Windows today, many of them originated as Mac apps, Photoshop, Illustrator, Quark and the whole early desktop publishing industry. Ironically, even the original MS Office apps, Word and Excel were Mac only... you have to remember PCs ran DOS back then... so in many ways, by being able to develop for Mac, Microsoft learned enough about WYSIWYG GUIs to cobble together Windows as a shell on top of DOS, largely copying the concepts, but implementing them backwards... they still got sued, though. Anyway... a bit off topic, but interesting historically..
Since then, Windows has caught up in capability, and both platforms run on basically the same hardware, so it's really a matter of taking your choice. To me, the OS's look and feel makes a huge difference, and once someone settles into Mac for a while, it usually feels more integrated, less edgy and jittery... that's the best way I can describe the feeling. More natural, a simpler interface that doesn't get in your way nearly as much - but... that's my opinion. Others are free to disagree, and more power to them.
Bottom line: for photo editing, OS really doesn't matter as much as color management and software, as well as memory and GPU power. But, for overall experience, OS matters.