As an underpants lover, I have been a slavish follower of fashion over the years Mother started me off in baggy white cotton drawers, then I rebelled - Y-Fronts, slips / bikinis / skants, boxers, boxer briefs / trunks, hipsters, I have tried them all as they came into fashion for at least a season each. But I always come back to slips / bikinis. They are the only underpants that mould and conform to my package, roomy man-shaped pouch, no gaps at the thighs, gently but firmly holding everything in place, Most other styles don't conform as well, leaving a gap at the side of the pouch, letting your cock fall out the side into the body of the garment.
Supermarket / chain store slips are as good as any, but you have to try a few before you find what's best for you. At less than £10 for a 5-pack, it shouldn't break the bank. For some summers now I have been wearing M&S's basic slips, I think at present £7.50 for a four-pack, get the right size and they fit perfectly - M&S are often larger than the label size would indicate.
However, I recently tried their ultimate microskin, polyester with lycra, and they are the best ever, a size smaller than I would expect gently moulds my (above average) cock and balls into a smooth package that does not jiggle about as I move, yet is not in any way crushed. At £17 for a two pack they are much more expensive, but not nearly as expensive as most of the "brands". And unfortunately, this season the choice of two pack has changed from 2 black or 2 different blues to 2 black or one pink! plus one dark blue. No, I am not an M&S employee nor a shareholder!
I would say that I have some Under Armour 23cm boxerjocks, that I sometimes wear in winter. The front pouch does not suit me, it is too small and my cock and my balls can escape, and get trapped at the top of the leg, so if it is cold enough for the long leg boxerjocks, I usually wear a bikini underneath. Unfortunately, going for a piss means going into a compartment and unfastening belt and waistband, unzipping and taking my cock over the top of both pairs of underpants. Mind you, when I am wearing cargos with stuff in the pockets, I usuallly do that in any case as the weight in my pockets tends to pull my trousers right down. Would'nt want that at a public urinal, would we?!