I boot into Windows for work since our whole stack is Windows-based and it's just easier that way. I agree that to a pretty large extent the OS doesn't matter when developing. This is especially true when everything is up and running fine. But there's the rub -- when things go south, that's when you find out what your preferred OS is.
Troubleshooting a recent virus/malware problem on Windows turned into rebooting countless times, Windows Update incantations, several malware tools, and so forth until the OS was unbootable and I had to wipe it and install everything from scratch. Knowing what I know about Windows and Mac, I know how much easier it would have been to deal with this problem on the Mac, not to mention that it most likely would never have occurred in the first place.
So, that's my two cents -- when everything is running the difference can be negligible. When you hit problems, the difference may not be so negligible anymore.
Troubleshooting a recent virus/malware problem on Windows turned into rebooting countless times, Windows Update incantations, several malware tools, and so forth until the OS was unbootable and I had to wipe it and install everything from scratch. Knowing what I know about Windows and Mac, I know how much easier it would have been to deal with this problem on the Mac, not to mention that it most likely would never have occurred in the first place.
So, that's my two cents -- when everything is running the difference can be negligible. When you hit problems, the difference may not be so negligible anymore.