Both are best but there is slightly difference between them that Microsoft is user friendly whereas Linux is not, on the other hand if we talking about virus then we will find that Linux is virus free but Microsoft is not.
I think it depends on what you want to do. For Backtrack stuff I'd use Linux But for the most part I use MS
I have use Linux for 6 months, I think it is awesome to manage file, free from maintenance, virus, more faster on loading, etc