This paper analyzes the vulnerability disclosures and security updates for the first year of Windows Vista and looks at it in the context of its predecessor, Windows XP, along with other modern workstation operating systems Red Hat, Ubuntu and Apple products. The author is Jeff Jones, Security Security Director at Microsoft.
Here are some of the highlights:
Side-by-Side Patch Event Histogram for Windows Vista and Windows XP
Summary Table for Windows Vista and Windows XP
That was comparison with Windows XP, now comes Windows Vista Vs Other Operating Systems
Side-by-Side Comparison of First Year Vulnerabilities for Windows Vista and Other OS Products
Patch Event Histogram for Windows Vista and Other Industry OSes
Summary Table for All Products Analyzed
To get the complete report , to see how the analysis was done, methodology and to check out the FAQ sections with questions like , "You work for Microsoft, so why should we believe anything you say? " and many more , check this download link.