Favorite Operating System

What's your favorite operating system and why?

Right now my computer is a 2006 MacBook my best friend gave me, it's running Snow Leopard, Wmdows 8 and Ubuntu, I can't decide which is my favorite. Ubuntu is the best for getting school work done (computer science major) but I can't help but love Windows 8. I like at OSX is unix based and works well with my workflow but the operating system feels like shit to me, even moutain lion.