3 cm makes that big of a difference? I could see it if it was a 64 wide or something. I think the characteristics of the board shape are having more to do with it than the length. Anyway, I'd split the board that you are going to want to ride. Which sounds like the Highlife. Shorter boards are definitely nice for the tight trees and such you'll undoubtedly run into when riding in the backcountry. It just makes your life easier. As far as skinning goes, either will be just fine. In fact shorter skis make you life easier on the skin track too. Especially if you are doing a lot of switch backs on a steep slope.