Yeah theres nothing wrong with windows for servers. For webhosting i would stick to linux based.. same goes for game servers. But I've seen great things done with windows operating system for LAN's. But if the operator dosnt know what they are doing as in the setting up a bad config on the server and running things they should'nt of course thats also going to make a server unstable. So you always have to be careful reguardless of teh OS

But any way back to my point, really as someone said you can use both. But i think you have to look at what supported features you need as to why you are going to have to pick one over the other. Do you have enough knowage to use the selected operating system or willing to learn... use what you know and what will work for you.