Pros:
Maces are cheap ... at least the simple variants.
Maces are bountiful. Read: you can still buy all variants from NPCs, unlike most other weapons.
Fighting with maces is easy to learn. Most of them don't have a sharp edge or piercing direction so you don't have to worry much about how to hold it. I believe this is reflected in-game or is at least in the skill description.
Maces do more damage against Kran and heavy armor, like many others have said.
Maces just have that barbaric look going for them. Yes this is a roleplayer advantage!
As for the discussion of weapons vs armor. In my humble opinion it should be something like this:
- slashing weapons most effective against light armor
- piercing weapons most effective against medium armor
- blunt weapons most effective against heavy armor
As far as I know there is no piercing variable on any weapon yet, though we do have piercing weapons like daggers, sabres and longswords. Also I think that axes should to become a combination of blunt and slashing, just like the claymore. The warhammer and spiked mace variants should be a combo between piercing and blunt.