5th Gen Fire Blast or Fire Fang?

I am sure the title Kinda mislead you. Anyway, here is the details. I play B/W and I have this Garchomp. Generally, Garchomp's SP.ATTK is Lower than its ATTK. So if I teach him Fire Blast (which I did), it wont be as effective as a physical attack. However if I teach him the physical Fire Fang, I don't know what difference it could make since Fire Fang Base power isn't as Fire Blast.

This is his Stats at lvl 65: HP:227
Attack:213
Defense: 135
Sp Attack: 138 ( see the difference?)
Sp Defense: 118
Speed: 192
His nature is hasty BTW....so what move

I believe Fire Fang would be a better choice because of the huge stat difference, but I'm not sure how much of a difference there would be.

Use Fire Fang on Swords Dance sets, otherwise Fire Blast will outdamage it since its main targets will be stuff with lower special defense anyway, such as Skarmory.