12's vs 15's

[audioholic 5,000+ posts]

what I meant was if you gave a stronger 12" sub more power, you could get as loud, or louder than a weaker 15" with lesser power.

Well I agree, but Im not sure how that is relevant. You cant give a comparison of 12's vs 15's based on stacking the deck in favor of one size or the other. That does not give an adequate comparison, it merely shows the extremes that can be achieved based on install differences.