Well each OS has a function or attraction that is very good but overall for me its windows
Well i think windows is personaly the easiest to use and most of the time is stable enough . I still use XP as i dont have hardware capable of running vista well and when i used vista lite it didnt have any function i used that xp didnt have and tbh i got over the new shiny interface after a week or too and so went back to XP
One thing i do like though is mac can be very good for multimedia editing work
As for linux well it is very good , and the best thing is its free . Sometimes finding drivers can be hard but if you buy well known brands then you are more than likely able to find some after a few hours trawling the internet
but it does everything windows can do but for free . And in my experience is much more stable than windows out of the box but using some dodgy drivers off the internet can sometimes cause problems
I also think linux is good for old machinees that arent capable of running any recent windows . It is also generally more secure out of the box