The jewish hammer is NOT right. A 12" kicker L7 has a sensitivity of 88.6db.... Many round subs have much higher sensitivities! This is an important spec. So you cannot say just because it is SQUARE that its louder!
Lets do some math here.
Kicker L7 = 88.6db
Alpine Type R = 87db
So, the kicker is slightly more efficient, and can handle more power, so the kicker is louder. But you cannot attribute this to the SQUARE shape, as many 12" circular subs have sensitivities of over 90db. 88.6 isnt really anything to write home about.