I've used Mac OSX, Windows 95 through Vista, and various versions of Linux through the years, and honestly the very best out of all of them is whatever one is best suited for what you want to do.

I would probably be a full-time Linux user if I could play all my games flawlessly on it, but as I can't, I use Windows a lot on my desktop. On my laptop it's Linux basically full time. I use Allie's macbook a decent amount and have never had any problem with the user experience. You just need to know what you're using it for.