Is it hilly in the North Cascades? I am assuming so. I ride in hills (Marin) and mountains (the Sierras) and I wouldn't consider riding anything but a triple. Not only do I not want to sacrifice on the hill climbing end, but I also do NOT want to sacrifice on the power end, and a compact double would force some sacrifice either way.

Weight is NOT that big an issue when you are talking about these sort of components (assuming everything is moderate to higher end to begin with). If I pee before the ride, I have made up the difference.

I coach cyclists for "tough" events. The number of people with compact doubles who come begging for options (i.e., XTR, etc.) is pretty cute.

ETA: I have a "throttle", too. (A Bonnie, to be exact! )