chaos as winter backpack
I have an old chaos (purple and black) that's a little smaller than the current model. I've used it a winter day pack, rock, ice and back country skiing pack and a non-winter backpack. I've had it maybe 10+ years and it's pretty much bombproof although the foam support is starting to get a little soft and the support isn't quite as good.
I bought the new chaos last winter and I'm very happy with it. The material is lighter than the old model but so far it doesn't seem any less durable. I've taken it on some pretty thick winter bush whacks and no damage so far. I do some solo winter weekend backpack trips and it's not quite big enough to carry my 30 below down bag, down parka and down pants, tent, stove and other personal gear. For a non-solo trip with some shared gear, I think I could probably get everything in there.
I also have a Chernobyl which is a great winter day pack.
I think, given the weight of the packs, you can't do much better.