I was examining the interaction between knights and their counter, spearman. Doing a quick assessment of equivalent age unit v unit, knight takes 5 hit in all ages to kill a spearman (rate of fire 1.38). Spearman kills knight in 8 hit in Feudal, 9 hit in castle, and 8 hit in imperial (rate of fire 1.75). Why is castle 9 hits? Is there something specific here? An additional +1 bonus damage to cavalry would fix the issue and bring it back to 8.
Also please double check my calculations. I ignore armor and weapon attack upgrades as they cancel each other out.