I upvoted you because Apple's drivers for Windows are notoriously bad, but the major impact is on user input (trackpad, for example) rather than on performance (in fact, Windows tends to perform better than OS X on a number of tasks on a given hardware configuration) so I think it would still make sense to run the test on Windows on identical hardware.
its not about speed its about power. if hardware isnt even instructed to go into sleep mode for example, there will be large differences.. which tends to happen on macbooks running windows.