Easily PC as it offers choice and freedom (unless it's running Windows 8 lol). Personally I choose Ubuntu (Linux) because it's open source, free and designed for people by people, it might not be as open as a lot of Linux OSes but it is pretty awesome!
Linux is the future, what with Windows going all Apple with their W8 store crap and Apple still being Apple there is a new opening for Linux to rise especially with Valve's Steam for Ubuntu and Steam OS which runs Linux coming out, it's early days yet though but I hope for the best!
