[Agema]

Chainmail might very effectively stop a sword slash - if the sword doesn't penetrate the links, it's effectiveness is greatly reduced - whereas a mace might crush whatever is below the mail. However, against an unarmoured target where the mace would still do lots of damage, the sword would cut a huge gash in the target. As the mace's relative effectiveness increases with more armour, it's more grounds to make it AP than higher damage. Although having argued that, I'd rather not see maces/warhammers with AP damage, more an increased damage, simply for game mechanics.