The orc armors are made from human armors.
Also they can drop unique shields and weapons.
Their weapon have high damage but low durability and is heavy and cost more fatigue to use – but on higher level it shouldn’t be a problem. It offers high damage and great ratio against armors.
The game is still half done at best and in actual state there is little reason to fight orcs at all. Unless you want to test your strength. Killing bandits is much more profitable and safe. Wait until they can actually raze settlements and take over strongholds so fighting them will be a must.
There are lots of reasons to fight orcs, once you have a lot of fatigue and two mercs that can spam the fatigue reducing ability, you can easily use the orc weapons. So fighting orcs to get their weapons is a must at the mid/late stage of the game. I generally try to have two shields on my front line (one good vs ranged and one orc metal shield for melee def (the durability is very high) and three weapons (crossbow (bolts pre-equiped, doesn’t cost you an equipment slot), spear and an orc cleaver/axe). The spear to keep up spear wall, the crosbow to pepper the enemy with bolts and the cleaver/axe to brutally slaughter anything that breaks the spearwall (with the cleaver/axe it is fast, even against orcs, while the shield wall with an orc metal shield takes a long time to take down)