Dragonborn beats the undead for raw power for sure. But the thing about the undead is, they never die. And every death is something learned. The dragonborn would have to forever contend with the chosen undead so long as the undead's will remained intact and they did not go hollow. The more the chosen undead kills, the stronger they get, until they can contend with practically gods. However, there is another little problem here. The Dragonborn has the soul of a dragon as well. So while their mortal shell can be destroyed, the dragonborn in essence cannot truly die either, since slain dragons can return to life so long as their soul is intact. I think we've entered into a hard fought stalemate.