I found this on another web board. Enjoy.
http://www.dslreports.com/forum/r20485758-Vista-is-the-most-secure-OS-of-2008
This paper is a compilation of vulnerability data for client operating systems for the first 3 month, January through March, of 2008.
Vulnerabilities and fixes for the following products are discussed:
Microsoft Windows Vista
Microsoft Windows XP SP2
Red Hat Enterprise Linux Desktop (v. 5 client)
Red Hat Enterprise Linux WS (V. 4)
Ubuntu 6.06 LTS Desktop
Apple Mac OS X 10.5 (Leopard)
Apple Mac OS X 10.4 (Tiger)
For January through March of 2008, Mac OS X and Linux users experienced the highest number of vulnerabilities as well as the highest number of High severity vulnerabilities while Windows Vista users experienced the fewest and the fewest High severity vulnerabilities.
Download the paper for full details:
http://blogs.technet.com/security/attachment/3055337.ashx
Of course the report comes directly from Microsoft!