While I'm looking for the same thing in terms of comparing specific IV/moveset combos vs. another, I can answer yours right now - Fire Blast will win out on offense.
Vs. a normal defender like Snorlax, Blast is going to give you another 6-7% DPS. You would literally have to be comparing like a 100% Flamethrower vs. 0% Blast
So without even knowing how those IV's you have are distributed, it doesn't matter - Fire Blast will win out