Like Tony, I love the blue label Krawlers (siped) in the snow. I'm not going to say they were the best but no other tire on many varied trails did better.
I've been out with guys that were running red Krawlers and they did suck in the snow, that said, what makes a good snow (or generally good NW wet trail tire) is completely different than a good rock tire. While obviously compound matters, the best rock tires have very few sharp edges and shallow lugs. The Krawlers that are used on at the comps would normally be considered a worn out trail tire up here. The edges are so rounded that mud and wet trail performance would be pretty bad.
Do do well in NW wet/snow AND the rocks, I think 2 sets of tires would be the ideal for best performance. The requirements are just too different for one set of tires to be really good in all environments.