They are both the same price.
Area of circle Pi time radius squared.
So in theory two nine inch pizzas have more square inches.
127 vs 113
But to truly decide, you'd need to weigh the pizza as there are such variables as toppings to crust ratio that are not standard, and your opinion on that variable.
For instance if you get a one inch crust on any pizza, the two pizzas aren't bigger in topping square footage.
77/127 vs 79/113
Which will result in more pizza?
They are both the same price.