I hate tight underwear so thats out, and loose boxers seem to try and sufficate my legs when I'm turing over during the night, so I have to fiddle with them regularly.

So I just don't wear any at all. Most comfortable.

If I'm at a mates house or whatever, then I still sleep naked, but I keep a pair of boxers nearby in case I need to visit anywhere. If they are going to rip the sheets from me whilst I'm sleeping then they kinda deserve what they get