Wool is my favorite for warmth up here in the frozen north reaches of the US. However that being said I have two enormous rolls of W&N currently in my sewing room so most of my quilts are done with that. It was -18 degrees F here the other night and our setback is to 60 on our thermostat at night. My "winter quilt" has W&N with open (not dense) quilting but what adds to the warmth is a wonderful cozy backing of flannel. The flannel adds warmth as well as keeps it from slipping around on the bed! I also have a light weight cotton blanket and flannel sheets under it lol - but the combination keeps me warm.