
I'm not sure as it's hard to draw any real-world comparisons between them. The Rohirrim seem to be Anglo-Saxon warriors on horseback, so having a real idea of how they would fight in a cavalry engagement is a bit of a guess. I'm pretty sure forming a shield-wall on horseback would be a bit of a futile strategy. Regardless of arms or armour, you'd think the Dothraki would be the better horsemen still being nomads, whereas the Rohirrim being settled, were not in the saddle as much. We might get a better idea if Martin finally decides to set the Men of Westeros against the Dothraki... but even then the Knights of the Seven Kingdoms are more akin to classic 'chivalric' knights (I use the term loosely...) whereas the Rohirrim I think would be much more mobile. I think an initial charge by the Rohirrim would cause a lot of damage to the Dothraki ranks, but following that in a general melee the Dothraki would have the better of it. So my heart says the Rohirrim and my head says the Dothraki. Saying that... I'm still in denial about the Battle of Hastings... so my views are to be taken with that in mind...^^