I've recently started playing BC and I noticed all the archers and crossbowmen have a missile attack of 5 and all javelin troops of 11. Now I don't believe all archers perform equally, in that case I wouldnt see any reason to use better archers than the dirt cheap ones. I have also noticed large differences in kills between different archery units.
Now I wonder, how do I know which archery units are better and by how much and why isnt this just displayed by a higer or lower missile attack value? Or are the differences between archers just that some can pierce armor or shoot at long range, whilst they have the same base damage?