I wouldn't run a Windows server, but at least it can manage a SYN flood, whereas MacOS doesn't have syncookies or similar (their version of pf has the syncookie keyword, but it seems like it only works for traffic that transits the host, not for traffic that is terminated by the host). Windows also has some pretty nice stuff for servers like receive side scaling (afaik, Microsoft brought that to market, or at least was very early).