My choice for warmth is wool. I spent a Minnesota winter in a trailer (not as ritzy as a mobile home) with only a flannel sheet and a vintage wool-batted cotton-covered comforter and was never cold. The next winter was in California, and that wool comforter was still perfect, not too warm, never sweat-inducing like polyester can be. Now I also love my wool-filled pillows; hypoallergenic, winter-warm and summer-cool, will last for many, many years.