I had to use some Mac OS when I was in college because we had Mac labs in the building where the majority of my classes was, and I had a couple classes in those rooms. Made me have to learn how to use a Mac a little bit. (And I had to really use them my last semester because I had to use Final Cut Pro for one of my classes.) I've considered getting a Mac of my own, but I decided to just stick with Windows.
I switched to Linux (Kubuntu specifically currently) because Windows 8/10 are terrible. Also I use Linux at work as a software developer and got rather used to it so I started using it at home as well.
Windows 10. Made the switch when I got a new computer whose motherboard didn't support Win7. It's pretty stable on my end, though I did have some issues with it on my laptop. Was already used to it from work, because we test games and most recent releases are optimized for it. The switch was mostly painless.
I did do a couple of projects on MacOS (as in I spent a couple months on OSX), but I wasn't a fan already and that didn't do any help.
I'm pretty deep into Windows at this point. I run a couple of Linux VMs but mostly a big Windows fan here. Being Microsoft certified also helps so maybe I'm sort of expected to say Windows. I would consider using MacOS though for my laptop, those new Macbook Pros are very pretty.