What is a good brand and style of briefs for a 15 year old teen?

Comfortable Brand: Style is individual. Support of the genitals especially the testicles may be necessary. If it is just comfort---to each his own. Some like no underwear, some like looseness like with boxers, others like a little more support like in boxer briefs, and then others like less such as briefs, bikini briefs or pouch underwear or thongs. Even jock straps. Just let the 15 year decide his preference.

Comfort: From a comfort standpoint, the same as you like. From an adolescent standpoint, choose cotton, no embarrassing prints, consider neutral colors. Consider the locker room.