I agree that both 3315 and 3369 are good choices. Both knights feature the most modern plate armor Playmobil has produced and good helmets.
I think 3315 may have the edge in most categories and he does look very fearsome. While his somewhat impractical arm armor and helmet crest could impede him in some ways and his stomach and lower back lacks any visible plate armor (perhaps strips of plate are underneath his surcoat?), he is otherwise well armored with plate or chain mail on his legs. He carries both a sword and an axe, albeit a slightly heavy and impractical double edged one. Unfortunately, he carries no lance, which is a severe disadvantage when facing an opponent with one, as he really has nothing to counter a lanced opponent and he may be unhorsed before being able to reach his opponent with his axe.
I think 3369 has better arm and body plate armor, but his legs are unarmored. He also has a lance, which is vital to combat, but unfortunately he falls short by having no other weapons. Once his lance breaks or is lost, he's out of the fight.
If one could combine these two knights into one, one would have a fearsome knight! Actually, it would be quite interesting to see these two knights go at it, but it would only be fair to give 3369 a sword and maybe 3315 a lance.