How many times must this question be answered..
Knights are for the mobs, and bosses that summon mobs.
Warriors are for the bosses.
Yes, warriors and knights can do both but a warrior can't aoe tank as well as a knight and a knight can't boss tank as well as a warrior.
Either option is fine, but both hold their own advantages.
Really? My Knight tanks just find on bosses, Maybe you should learn how to play the class better? My Knight has never ever lost hate on bosses, yet I see warriors I party with that do all the time.
Solution to which is better is simple: LEVEL BOTH they both use the same gear, and since warriors +patk/matk passive is for axe's and there are no 1 handed axe's, you can use same weapons for both. Why limit yourself to 1 of the 2 when you can easly level both?