If the heading sounds weird, it's not because of the odd-choice of words. It's because Microsoft suddenly realized that its Vista operating system was the most secure OS out there. Why? Because Vista had the least number of vulnerabilities in its 6 months of availability. Too bad non-Microsoft security experts don't agree.
This "analysis" claiming Vista's superiority over Mac's OS X and Linux distributions (in all matters security), came from Jeff R. Jones, a Security Strategy Director in Microsoft's own Trustworthy Computing group. It seems the only people praising Microsoft these days are Microsoft employees themselves. But wait. I don't need to be so cynical, when others can do much better.
Fact wise though, Kristian Hermansen at Full Disclosure has debunked the report in detail. The crux of the matter is what it always is. First, Microsoft compared plain vanilla Vista with a fully-loaded competition (and we *know* how vanilla a Microsoft OS can get). RHEL cannot be held responsible for the 100+ vulnerabilities in software such as PostgreSQL, MySQL, mailman, squid, and emacs, which aren't even installed by default. Second, Mr Jones fails to mention the Microsoft policy of not disclosing vulnerabilities that were patched before anyone in the public noticed them.