Debian Linux.
Windows sucks. Not only does W10 still need a reboot after every friggin' update it installs, it also wants to install software all the time that I don't want and don't need. I really really miss apt-get on Windows. One command and you update all of your software while on Windows every fuckin' software has its own "auto-updater" or some shit that is constantly running in the background and eating up your resources. Last but not least, Windows 10 spies the shit out of the user. What was a trojan horse back in the day is now an official feature of Windows. Hooray, I guess.
Mac OS is quite alright, but just not at the same level as Linux.
Official member of VGC's Nintendo family, approved by the one and only RolStoppable. I feel honored.