While the Leather Armor leaves your footmen with more Defense Skill, the actual tradeoff is that Footmen in Leather have an overland movement of 2 instead of 1 and cost 11 resources instead of 20.

• 皮甲使你的步兵拥有较高的防御技巧，作为交换，皮甲的步兵的地图移动力为2而不是1，需要11单位的资源而不是20。