Having been a member of this Board for almost a year now, I've learned that I'm a total outlier on this topic, but I still recommend using fleece as a batting if you want a really warm quilt.
I made a quilt for my elderly mother when she just couldn't get warm last winter. She hates the feel of fleece, but it was the warmest fabric I could think of. So I pieced an all-cotton top and backing for the quilt, then used generic white fleece (purchased with a coupon) as the batting. I did simple SID quilting (fleece doesn't need much) and the result was a lovely WARM quilt that Mom really used.