Full mummy style sleeping bags present many issues that many of us are well aware of and ones that aren't that well known. Unless you can sleep on your back, like a mummy, and not move through the night you are likely to end up with your ear sticking out of the face hole and your face smooshed into the side of the hood. That is if you spin yourself inside the bag. The other option is to roll the whole thing with you, which is somewhat difficult to do without rolling off your sleeping pad. Even if you can do this effectively it isn't doing your down fill any favors. When you roll over on one side you crush all of your delicate down on that side, which is not a big deal till you roll over to the other side. Then you are hoping the down you just had compressed will loft back up and keep you warm as it is now on top. This is not the best scenario. It's much better to keep your sleep system stationary and move inside it with a warm hood on your head. My draft collar cinches down against the hood to keep drafts out. Additionally it provides an opportunity to make some gear dual purpose. For instance instead of carrying a hat and a big hood on your mummy bag, just carry a hood that you use during the day and night. Or carry a hat and a light hood so you can double them up on cold nights and have a regular hat during the day.
