Where lead is concerned in the 16ga the fact is handles a square load perfectly in the 1oz that about handles anything a typical game gun is likely to encounter a 12ga which is typically heavier where correctly proportioned guns are concerned, the English 1 and a 16th oz 12ga game load and in 16 ga were 15 16ths of an oz. The 12gadespite its theoretical advantage never dominated the 16ga on the pattern plate or in the field, the lighter better proportioned gun and square load pulled it through very well, although i agree the above features are not MYTHICAL VIRTUES you can not simply cast them off as irrelevant or false these are the observations of many and even recognised authorities on shotgun ballistics old and new from Burard and lord washingham to gough Thomas and Bob Brister all quote the square load and at least the first two directly quote the 16ga as fielding such virtues.
In Europe notably Belgium and former soviet states and Russia 16Ga enjoys much more popularity and these nations seemed to have dodged the magnumitis that has plagued us in the west.
!6ga can indeed match a 12ga in its field of use which is as a game gun, to compare it to a 3 inch or 3.5 inch 12ga is folly less so where the 3 inch 20ga where only availability of ammo and some time slightly slicker handling 20ga guns can be encountered, on the pattern plate or in the field the 16ga with a 36gram load will generally dominate the 20ga magnum and its long case.
16ga are mot mythical but they are not at any dissadvantage worth mentioning to comparative 12ga loads, and most certainly not the 20ga which fails on all but available practicality but not on performance. best 20 ga loads are 21.. 22 gram the 28 gram 16 load in its square configuration is the one to beat.