I would generally recommend based on my experience with sized m l and xl sizes you stick to the size charts recommendation erring on sizing up if cinching the bottom is important to you or not if its not

Ok so these things are obviously awesome

More need not be said about that but one thing that can be a bit confusing is the sizing particularly if you are looking for a

Big enough to cinch up the end and sleep but fitted enough to not be awkwardin the way when doing stuff