While I have not played the Korean nation yet, I do have 2 accounts and use the British and the Japanese. I am thinking of changing my Japanese nation to something else and have been researching this. As far as Archers go here is what I have found. This is only for the Medieval Age, since that is where I am. BTW, I used this site to find my info.,
http://dominations.wikia.com/wiki/DomiNations!_Wiki
For level 4 Archers, all have the same Health, 156. Training time also the same, 50 sec, This is the breakdown.
Archers Korean Archers British Archers Chinese Archers
Damage Per Second 18 26 20 24
Damage Against Infantry 74 105 80 96
Range 4 4 5 4
Cost 210 200 210 210
To me, for just Archers at this level, I would pick the Koreans.