General

DrKs level up faster, and heroes are stronger, but only with ACA 10. Both of them can cope without the UA skill in 3rd job. Dragon Knights can use fury, and Heroes can use coma. Brandish is better than soul driver to charge up orbs for coma. Both of them lack an AoE skill without cooldown. Both of them will benefit from being a UA, just like any other class. Heroes use a ton of pots, keep that in mind.

UA Hero definitely outweighs a UA DrK in terms of 1v1 attack. Drks have more mobbing skills, but Heros make up for it with their attack buffs. Unless you think you're going to die using a Hero, which I won't lie they're not the best in terms of defense, I'd choose a Hero.