Linux is best for what it's made for, same with windows or os x.
Linux is secure and multi-user. It's very customizable and you're not stuck to anything you don't like, like IE.
Unix is hardcore. It's barebones and requires a true ninja to run the way it's meant to be run. (our united bimmer server is on unix- FreeBSD).
OS X is nice for video editing and multimedia. It's stable and easy to use, but lacks the control other operating systems allow.
Windows has solitare. End of discussion.