I think it depends on what you're developing. It seems to me as well that the majority of devs these days use Macs but it may just be the industries I've worked in or near for the past decade. If you are building web apps that are going to be deployed in a Linux environment then I think MacOS is just better suited than Windows due to all the command line tools, vm tools, design tools, and IDE's. I recognize my bias. I guess Windows is doing a better job of providing a *nix like environment for development but I'm not switching anytime soon. The only drawback for me is testing things for IE and the fact that we STILL have to test things for IE.