Microsoft's Windows Vista recorded about half as many vulnerabilities in its first full year of availability as Windows XP did in its opening 12 months, company security executives said Thursday.

In an update to earlier 90-day and six-month reports, Jeff Jones, a security strategy director in the company's Trustworthy Computing group, cited vulnerability and patch statistics to show that Vista logged 66 total bugs between November 2006 and November 2007, 30 of which had not yet been patched. In the first 52 weeks Windows XP was in user, on the other hand, it was pegged with 129 vulnerabilities, 54 of which were not fixed by the end of that 12-month period.

Others at Microsoft used Jones' statistics to claim that Vista is more a more secure OS than XP. "I think that it's fair to say that Windows Vista is proving to be the most secure version of Windows to date," said Austin Wilson, a director in Microsoft's Windows client group, in a post to the Vista Security blog. "Our investments in SDL [Security Development Lifecycle] and our defense-in-depth approach to building Windows Vista seem to be paying off."

Wilson touted Internet Explorer 7's "Protected Mode" -- a sandbox-style security provision available only in the Vista edition of the browser -- and Vista's own User Account Control (UAC) as reasons why the OS is more secure. "Of the 23 security bulletins that have been released for Windows Vista through January 2008, 12 specifically call out a lower impact for those running without administrative privileges," noted Wilson. "This is a great illustration of the importance of User Account Control and why we included it in the product."

But numbers don't tell the whole story, countered a pair of security professionals.

"As a lot of people have said, Gartner included, [corporate] switching to Vista has been a slow process," said John Pescatore, the research firm's security guru. "Microsoft has said all along that Vista would be a big leap in security, and it's been on that drum beat. Everybody does that. Oracle, Sun, Red Hat, they all say that they have fewer patches than the other.

"But Vista is definitely a major [security] improvement over XP."

Andrew Storms, research director at security vendor nCircle Inc., agreed. "The year-one for Vista and year-one for XP clearly show that Vista has had fewer vulnerabilities than XP. That's a good sign for Microsoft and the enterprise -- and consumers."

Even so, both Pescatore and Storms question the worth of bug counts, as well as some of Microsoft's measurements. "More important than the number of vulnerabilities is what attacks are targeting and how much pain there is in entering patches," said Pescatore. "That should be the real measurement."

In other words, a vulnerability in Vista or XP should not be treated as the equal of one in say, a Linux distribution. The former, because of the widespread use of Windows and much greater interest on the part of attackers to exploit the OS's weaknesses, must be patched without delay. The latter? "For most companies that use Linux on the desktop, they can patch in a much more leisurely fashion," said Pescatore. That's because they know the likelihood of an attack is slim.

Storms came to a similar conclusion, but for a different reason. "Outside of the Vista-to-XP, comparisons are a moot point," added Storms, referring to the section of Jones' report where Vista's vulnerability count was compared against Mac OS X, Red Hat Enterprise Linux and Ubuntu Linux. "You just can't compare Vista to Linux," said Storms. "There are simply too many variables. I'd argue the same for Mac OS."