Well, im assuming that you already know that you cant just switch a server over to linux, it requires a complete format etc. Also, it depends on what distro you are looking at and which features you need, if you are talking about your home server with all your computers on the domain, then a windows server is probably a better option. As far as webservers go, linux is what hosts the majority of webpages out there, and i prefer it to windows for web hosting.