I use the courser about 99% of the time for the reasons stated above personally. Speed is the biggest weapon and defense a horseman has online. However, I do use warhorses from time to time but only when I know I will be fighting in a somewhat confined area because you can just waltz up to spears and pikes if you arent going full speed and just take the hits, good for horsebump etc. If you are in an open field or area though, just stick with the fastest horse you can afford.