I haven't done cold weather survival yet, but I have researched it some, and this is what I have gathered, YMMV. There are trade offs here. The wool blanket is heavy, but if you use it as Canterbury does, it also doubles as a pack and cloak, spreading its weight around. The main advantage of using a wool blanket is that you can use it in conjunction with close proximity to a warming fire. The fire is great, as it will dry you if you are wet, and is relatively quick to set up, but requires alot of work in the form of wood gathering, and maintaining the fire, and some knowledge of firecraft and site selection, also a problem if the wind changes. A passive shelter, is generally more bulky, harder to set up, less comfortable, harder to keep dry in, but more wind resistant, rain resistant, and properly done, can survive colder temps. If I had my way, I would try to do both methinks, first a warming area with fire, and then a nearby insulated shelter in case the weather turned nasty.

Some thoughts,

C. Rowe