https://forums.elderscrollsonline.com/en/discussion/232480/optimal-weapon-and-trait-combination-for-2h-and-dw#latest

It is kind of old, sharpened was a percentage penetration instead of flat, but it answers your question.

Upon reading closer, it might not answer your question, I am going to leave it though.

So the difference between swords and maces is that maces have to penetrate around 2500 armor on a pve mob, around 3k armor on a player, to be more effective then just a flat 5% increase in damage. Or around 1300 or 1500 armor for a single mace vs a single sword, which is 2.5%.

So as you ask, figuring out how the game calculates the penetration is important.

After a bit of searching, I found this-

Dagoth_Rac wrote: »

There are two kinds of armor reductions. Personal armor piercing, which leaves mob armor the same but lets you and you alone ignore some of it. Sharpened and the passives on Mauls/Maces are like this. And mob armor debuffs, which reduce mob armor and allow everyone to hit mob a little harder. Things like Major/Minor Fracture, Night Mothers Gaze, Alkosh, Crusher Enchant, Sunderflame set, etc., debuff enemy armor.

The formula is:
((Mob Base Armor - Mob Armor Debuffs) * (1 - percentage penetration)) - Flat Penetration

In your example:
((Mob Base Armor - Major Fracture debuff) * (1 - 0.20)) - Sharpened penetration

So the tldr: if you don't have major fracture on the target, mauls/maces are better, if major fracture is on the target, mauls/maces and swords are about even, if you have anymore debuffs, IE NMG, alkosh, even a crusher enchant, swords are better.

Note that the debuffs are skills that benefit the whole group, so armor sets like TFS and spriggan and kraghs are calculated after mauls/maces percentages, as is sharpened.