Me! - In my experience, including time spent in the saddle as working cowhand, it's the most comfortable belt for day in and day out wear, the reason that the 19th century working cowboys preferred them. Time period though is a factor though and they weren't heavily used until around 1880 and after. Also body shape can play a part in whether they will work best - of course this should always be a consideration no matter what material is used. For some one with flaring hips, such as most women, they can be the cat's meow since they mold better to ones figure and generally DO NOT dig into the hips.
Generally I use 3/4 ounce, but you can go to 4/5 for a bit "firmer" belt - the best being closest to 4 oz. When building them, especially with 3/4 oz and using slotted loops rather than sewn, I will at times glue a 2/3 oz liner inside only where the loops go with about a 1/2 overlap. This gives a bit more "body" for the slots, but still leaves the bottom edge of the belt and the other parts flexible. I skive the edges so that the liner doesn't really "print" through. Even with the extra liner they are more moldable than heavy single thickness. Money belts are by far my number one seller.
The only other style I wear and my number two seller - although recently my number one - is the single thickness Indian style tack belts - made from well oiled harness leather they have a bit more give than "standard" veg tan belts.
While "softer" belts can work for the folks doing the "speed thing" a heavy lined belt is probably a better rig - again depending on body build, shooting style, and needs - presumed or actual. Then again the MB tends to mold to ones body shape so at times can be the better choice.
Of course being an unreconstructed maker of 19th century period pieces only - that colors my way of looking at things......