I found a realy nice pdf on the web that showed the results of a responsiveness test between windows vista and windows xp. It provides detailed information about the tests that were done and also confirms that responsiveness between both the operating systems doesn’t differ that much as Microsoft would like us to believe. In fact even when there are differences they are small differences.

Check it out: http://principledtechnologies.com/clients/reports/Microsoft/VistaXPBusResp.pdf