Armor gives damage soak (some amount of damage has no effect) and damage reduction (rest of the damage has reduced effect). Soak and reduction values are different for each type of damage but the same for all armors. Damage is rolled from 50 to 100% of the listed weapon's damage. Armor also rolls from 50-100% of listed rating. Result is damage roll*(1-soak*armor roll)*(1-reduction percentage). Never got clear on when modifers like speed and headshot come into play. The 6 soak and reduction numbers are listed in the .ini file.
Assuming none of them changed for Warband, against the typical range of armors, 6 blunt = 7 pierce = 13 or more cut. Swords look cool and devastate farmers, but warhammers are for the professionals.