The report that came out a while back saying basically how Vista has had hardly any security issues and Linux has had tons has been, debunked by insecure.org. First of all it's shocking that someone with interests in Microsoft would see less vulnerabilities and someone with interests outside of Microsoft would see more. Shocking. Next you'll tell me that statistics can be manipulated!
So read the debunking, and read the original report and commentary over at OSNews.