Well it all depends on what you plan to do with your mac. If you are into video and photo editing as well as making DVD's, that sort of stuff, then you will see a difference between Core Duo and Core 2 Duo. Core 2 Duo would deffinately process information faster, but the difference will not be that big. Maybe a few seconds or half a minute deppending on how much information is being processed. If you are only into typing up reports, surfing the internet, and so on it really doesn't matter which one you go for. If I were you I would go for the Core 2 Duo since you are at this fork of the road. You never know, you might end up liking video and photo editing. For that reason alone you might as well get the Core 2 Duo while you have the chance.