I am sure it varies with sleeping styles and conditions, but that is my experience as well. For me a slim cut bag is warmer and more versatile than a quilt. I zip it open and use it like a quilt in warmer conditions. When it gets colder I zip up and pull the drawstring tight. In that mode I find it warmer than a quilt due to the lack of drafts and the slim cut. I actually have not found a quilt that works for me that isn't as heavy or heavier than my Mountain Hardwear Phantom 45, which is one of my very favorite pieces of gear and has served me well in a wide range of conditions backpacking and bike touring.

I wanted to like quilts, but have not found them to deliver the versatility or the weight savings they promise.