I have been working with UNIX for almost 20 years now and I am partial to it. I really don't know about what the thresholds of windows would be with regard to networking. I can tell you though that you will get a lot more "bang for your buck" with Linux. The only down side to Linux is that you really need to be proficient with the OS before you can really do anything meaningful with it. It isn't like windows in that regard. Everything needs to be configured.
Frank