Most standard-cut name-brand men's briefs are now sold by the letters: S, M, L, XL. This includes Hanes and Fruit of the Loom (who also use the fine old BVD brand for a lower-priced line). For example, Large (L) is usually size 36-38. Some store brands of briefs are still sold by even numbers. These numbers correspond to waist size in inches.
Sizing by the letters saves the manufacturer and sellers money, because they need to produce, supply, stock and display fewer sizes. However, this can mean the customer cannot find clothes that fit. Size M (32-34) briefs and size L (36-38) are effectively size 33 and 37, respectively. These two sizes are seldom sold by the numbers at all, so there is a fundamental difference. Furthermore, a man with a 35-inch waist is particularly poorly served.
Legband. The issue, in this case, is not the big, tough waistband, but the legbands. (See the pieces of rubber and enclosing fabric cut from an old legband in the adjacent photo.) For a 35-inch waist, the size M leg hole will be too tight, while the size L leg hole will be too loose. Furthermore, for a 34-, 36- or 38-inch waist, sizing will be imperfect by the letters, but spot on by the numbers. Only for a man with a 33- or 37-inch waist will sizing by the letters be better. Accordingly, I now wear "berkleyjensen" briefs, sold by the numbers at BJ's Wholesale.
History. When Hanes started selling by the letters, my waist size was 34 to 35. I searched around and found the Lanesboro brand at BJ's Wholesale. Initially, they had a seam in the back of the waistband, covered by a sewn-in label. After a while, they omitted the label and printed that information on to the fabric at the back. This was fine, presumably a savings in manufacturing, and possibly better for me. Then they moved the waistband seam to the side, a problem: when dressing in the dark, it was no longer easy to find the back of the briefs.
This was the point where I tried Jockey briefs again. These are the black ones in the adjacent photo (smaller after a couple of washings). They are cut differently, although you can hardly tell from this outside view.
If you compare that to the inside view in the second photo, the Jockey cut is different on the inside and the outside, where the fly opening is horizontal. In contrast, the standard "BVD" cut (white) briefs are basically the same, inside and out, except for the fluffy inside of the waistband. I recently wore standard briefs inside-out for a whole day without knowing! The Jockey cut may appeal to men who always wear them; they are annoying, after a lifetime of standard cuts. (Munsingwear offers yet another cut.)
Every once in a while, I get a free 3-month BJ's membership. More than two years ago I wandered around BJ's with my new card and found the new "berkleyjensen" store brand briefs. They proved to be just right, with the seam in the back, so I went back for a second and third pack. One of those still-new pairs is in the adjacent photos.
July 2020: Full Cut vs. Low Rise. We visited my daughter's family in Vermont, and I failed to pack any briefs. I picked up some Stafford (JC Penney brand) briefs, sold by the numbers, at a store-closing sale. I was surprised to find that these "full cut" briefs were taller than standard cut. The new, blue pair shown is 1.25 inches taller than new BJs briefs, just laid out. In practice, the fabric stretches more than that. Both brands shrink about the same amount, when washed.
If you are slim and wear your belt above your hip bone, this may not matter. I wear my belt below the hip bone, which puts the top of standard briefs right at the top of the belt — a particularly comfortable situation. When new, the complete waistband and more of the full-cut Penney briefs were above my belt, which felt unusual.
A check online shows that JC Penney also has "low rise" briefs, which I did not notice in the store. These appear to be standard cut or a little lower.