I guess there's no surprise that I vote for Linux
I prefer it for stability, performance, security and because it just makes my daily work easier and comfortable. No need for antyviruses, the firewall is embedded in the kernel itself, has all the programming tool I could ever need.
It would be great if for a change we would not turn any Linux thread into a fight, but rather each speaks about what he likes, instead of what he doesen't like. Here is your chance, let us know what you *do* like, and why.