Most Helpful Guy
Lore-wise, side with the dragon. You are at this point renowned as a dragon-slayer, and likely capable of killing him if need be. Since the need be isn't there, you can take the opportunity to learn abilities from the teachings of a creature whose race was responsible for developing said abilities. Unless you want some neckbeards glorifying abilities that you can grasp far faster than they can.
You're fuckin' Dragonborn, my friend. Live it.