Potency vs. combustion

[Guevara1]

I have a superior potency dagger that says it increases the effectiveness of all spells by 50% (I think). I also have a superior combustion item the inceases the damage(?) of fire spells by 50%. Are they doing the same thing for my firewall or am I not understanding something correctly?

[Harbinder]

Same thing, they don't stack.

Find yourself a superior fire LORE dagger, and dual wield that with a superior potency dagger.

[Jakylpops]

The only real reason to use a combustion over a potency item is that they have a lower level requirement, and can reach higher spell levels (I have quite a few Superior Combustion VII items, but have yet to see a Superior Potency VII item).