Like most of the others, I prefer the sleeping bag because it moves with me. I've tried a quilt, and it worked great in the summer. But I found that as the temperature fell, I would end up with gaps as I moved, or if not an actual gap, then I'd lift it just enough as I moved that all the nice warm air escaped, and I had to re-heat that spot. Also, the lack of a draft collar seemed to matter to me; I couldn't replicate that with a quilt.