IMO, Captor Chivalry is easiest to get. Ransom won't work all the time and I will be forced to execute the prisoners (should get another chance).

I got Battle Chivalry once when I won a fairly easy battle (I had 9 Knights unit vs full stack of peasants and militia). I couldn't chase down the routers because I was out numbered 2/1. As soon as the enemy unit run away, I had to redirect my unit to attack another target. In the end, I only kill nearly 300 (of over 1000 enemy troops) and captured about 50. I will try again to see if I can get Battle Chivalry again.