Feeding a crowd? You'd think that ordering two 12" pizzas would satisfy more people's hunger than one 18" pizza but geometry proves us wrong! Don't ask us to explain the math behind it...please see below.
One person points out that if you're a crust-lover then two 12" pizzas would give you more circumference and therefore more satisfaction. We'd agree if it were STUFFED crust!
But we should also point out that if you have the option of comparably-sized rectangle or square pizzas, you'll always get more with those.