I would say boxers in most cases, sometimes briefs. But you know what i also think? Girls who prefer briefs are still ok with boxers and girls who prefer boxers think guys with briefs look like dorks So play it safe.
Honestly, "real" men in general probably can't pull off this exact look, and this is my teasing way of getting back at the few guys on the forum who compare "real" women to the fake Hollywood image of what women are supposed to look like.
In reality, any man that is in reasonably decent shape looks good in just about any kind of underwear - my personal preference is still boxer briefs or boxers, just because I like the way they uh, accentuate some assets without being glaringly obvious. <blush> As long as the gut doesn't hang over the elastic, it's all good to me.
Almost all women prefer boxers ... despite that ... we for the men will learn to like briefs (hehe although I do slip boxers into my honey's holiday presents every year lol ... but thats just cause boxers have alot more funny sayings and pictures on them ... briefs just dont have Scooby Doo and holiday scenes like boxers)
I was going to answer "Naked", but then I realized it was about men's underwear.
Personally, I have all kinds mentioned, and I haven't too much preference, though cheap boxers are annoying. Boxer briefs are nice, but they tend to keep me too warm -- fine for winter, but not the summer at the office. MUST HAVE briefs for running.
Boxers are horrid! They are uncomfortable and dorky looking. I've been a long time swimmer and am accustomed to wearing a Speedo. Boxers for a swim suit look incredibly stupid to a swimmer, so I would never wear them for that reason alone. I think guys who can't wear a Speedo or briefs are just insecure. !