There's very little difference between an oval and a tight square. The benefit to the tight square is you can not only level your wings on crosswind/base but it's also easier to raise the inside wing for lookout if you have a high wing (or a low wing on the final turn).
I agree with what thing said about staying in gliding distance. This is surely the most important factor for circuit size, and it's strange that so many flyers seem to give it so little thought.