Smaller numbers are better. It's not always  true in RPGs, but it is generally true. It's easier to work with in terms of calculation, but perhaps more importantly it makes it easier to intuitively gauge the significance of the numbers. You can feel the impact of a +1 on 1d6 more than you can on a d20. The older I get, the more I appreciate smaller numbers. The art quality in OD&D may be lacking, but the art direction  was pretty dang good. Number creep started with Greyhawk, continued in AD&D, really took off with 3e, before being scaled back a bit in 5e, with its notion of "bounded accuracy". 5e's notion of bounded accuracy still yielded a greater inflation of numbers than Classic D&D (Holmes, B/X, BECMI, Cyclopedia) which held back a bit on that front but still had slightly higher numbers than pre-Greyhawk D&D. One of the most obvious parts where number inflation took off is hit points. And in this regard, I quite appreciate the HD scale in OD...

There are three armor types in classic D&D (B/X, BECMI, Cyclopedia). Leather (AC7), Chain (AC5), Plate (AC3).  In terms of classes, fighters, elves, dwarves, halflings and clerics can use all armor, thieves only leather armor and magic-users no armor. This is important, because this frames why people wear the armor they do. Why would anyone wear leather armor? Because they can. That means thieves. Thieves can wear leather, magic-users can not and that gives thieves an advantage. It's also cheap and only weights half what chain weighs. There are no real downsides to wearing light armor over no armor, except weight. There is rarely much reason to wear chain armor though. Plate mail is only slightly heavier and pricier and any class able to wear chain can also wear plate. In other words, chain is almost never a meaningful choice. It's going to be all Clyde Caldwell for this entry. It's All AC5, baby. So maybe we should find some reasons to make the choice between chain and...