We are partial to bibs or mountaineering, back country skiing and climbing. Body movement sometimes put pants into positions that are uncomfortable or hamper movement. One way around this is to have a suspendered pant. An option we have used and liked alot. The problem this does not fix is preventing air and snow from getting to the body.
Jackets can ride up, exposing inner layers.
We prefer pants for fast and light activities. Our buyer used a pant on K2 because of the weight savings. Ounces sometimes matter. He also uses a bib when guiding on Denali because it is warmer and more comfortable with a pack. Some pants are heavy and durable.