If part of the trip is spent in winter and/or high altitude, one good warm jacket to deal with extreme cold is essential. The biggest debate seems to be between down jackets and soft shells. Down Jackets Down jackets vary in quality and warmness. There is no standard in "warmness" since individual fitness levels, health, wind-chill factor, and activity affect how you will feel the cold. Like down sleeping bags, down jackets will have a "fill" rating and percentage of down vs feather. The higher, the warmer, generally speaking. They are usually quilted so that the down is more evenly distributed. Advantages: The warmest material compared to wool and synthetics The lightest fill material available Packs down into a very compact package. Disadvantages: If it gets wet by rain, snow, or sweat, it becomes useless for warmth, becomes very heavy and takes ages to dry Is suitable only for the very cold, so it has a limited range of use. Soft She