Briefs in public or when I've been awake a long time. Boxers when I come home from work and change clothes or on weekends after I wake up and shower and I'm just lounging around the house. Used to never consider wearing boxers, I don't like the uncontrolled nature.
Oh yeah, before moving in with my girlfriend, it was always briefs, I didn't even own any boxers. When I lived alone, I went naked around the house or wore a pair of shorts by themselves, but usually if I had anything on I was also wearing briefs. I'm sure you can guess why boxers became bearable for me when I moved. :-D