For hand quilting, I have gotten Thermore lately. It's 100% polyester, but thinner than anything I have ever seen. Hand quilts like a dream. I am quilting my Dear Jane with it in it. I decided to try it as there is almost as much fabric in the seam allowances on the back as there is fabric on the front. Wanted really thin batting. For machine quilting - Warm & Natural or Tuscany Collection, especially for a wall hanging. I want the wall hanging to lie nice & flat.
Polyester used to be the bees knees for hand quilting, but then along came machine quilting & polyester just doesn't lie nice & flat or smooth.
By the way, the warmth of a quilt usually depends on the pockets between the stitching to form little insullating puffs. The warm body heat is trapped in them, keeping you warm & keeping the cold air out.