I will always have a soft spot for Windows 7, however it's aging rapidly. Windows 10 is faster and will continue to be supported for a longer period of time. I still use Windows 7 because I have a big issue with Windows 10's philosophy. Microsoft thinks of Windows 10 as a service and not as an operating system.. that's completely retarded IMO. I use Windows 7 still, but my primary OS is ElementaryOS (Loki).
10 is the best in resource management and running light. 7 was great for it's time but its a hog just like XP was. I'd say for Windows based systems, 10 Pro is the way to go. Anything else, Linux Mint or CentOS. I had a few iMacs and Macbooks over the years, I love OS X or Mac OS as they call it now but there simply was too much I had to tweak to get things to work the way I wanted. Today, Mac works on almost everything a person would need it to, including some of the newer games as well as most Indie.
Coming back to this thread because now I have a MacBook Pro.
Windows 10 is pretty good (what I use on my desktop), but OS X is also pretty good. I won't really go into details on what I like about OS X. But I definitely don't feel as if I am limited by using it compared to when I use Windows. The only very obvious limitation is that there are some applications I cannot use because they don't have OS X version. However, I've easily replaced some of them with similar alternatives. Such as using Captured instead of ShareX (but I would really hope ShareX comes to Linux some day).
I know this was meant for Windows, but I thought I'd share the opinion anyway.