I actually ran similar tests on a dual boot mac with Leopard and XP on it a while back. The Mac OS was configured so that you had to manually log on with a username and it also had a Skype klient that loaded at startup. The XP was extremely vanilla without any user accounts or anti-virus. The Mac was noticeably quicker. The difference in startup time up was silly. XP needed 1 minute 45 seconds before I could start surfing in a webbrowser, MacOS 37 seconds, not to mention that to start working from sleep was a matter of a second in MacOS and something else entirely in XP.