Briefology: the science
There's a lot of garbage out there regarding men's underwear. The first is that wearing just about any brand will give you six pack abs or will make you sexy. The second is: one sizing fits all, as long as your waist is in the given range. Given all the confusion this creates, it's no wonder that most men either freeball or wear boxers, neither which work for me when I'm wearing a suit or trousers.
I'd like better science on well-fit underwear. I'm small waisted which doesn't mean that I'm skinny, but short-cracked is a better word. If I wear boxers, they ride up to my navel. Then there's the issue of the bottom of the butt riding up, not to mention pouch size and accessibility. Sure you can choose underwear based on how "sexy" it is, but if it fits your physique and is comfortable, chances are you're glowing and it's sexy.
Since briefs / men's underwear have such an "unmentionable" status, they will likely continue to be ill fitting and universally proclaiming six pack abs for all.
I think a lot of underwear is cheap and nasty. Hence they don't fit well. Of course, expensive underwear doesn't necessarily fit well either. Some guys like to go commando, but then that assumes their pants fit well. Not something I would do. I like wearing boxer briefs these days. They seem to fit me well enough. But it can certainly be hit and miss.