Other operating systems do security very well with far fewer resources. This isn't the opinion of a lay person or one of the idiot tech columnists, it's the opinion of a Windows developer.
I must disagree with your contention that you can provide security without a performance hit. It’s a fact that all virus software impacts performance. Security must be considered at many levels and at some level, particularly buffer overruns, you can have improvements without performance hits. But that is just no true overall.