I'll give you the short version. Heavy armor lets you soak a lot of hits, but you get hit more often. So you can ignore commoners with daggers, but you are more likely to get hit. So if something deals a boatload of damage, you are in more danger. It was fun, but heavy armor looks worse and worse when you get into late game. If an enemy can deal 50 damage and you stop eight, it is not really a cool trade. AC pays off better when the damage numbers start to get high. Monsters with high damage full attacks will flatten you. Against common, low end enemies and monsters it rocks.