As a side note, lateral balance may not sound like it should have an effect, but it does.

I spend a LOT of time eeking out every bit of turning radius I can get from my planes. It's not uncommon to be able to add 3-5% to my elevator deflection after balancing laterally, sometimes more. It shows up even more dramatically in the negitive direction. An out of balance plane really suffers when it comes to tight outside loops and turns as well.

The reason is simple. If one wing is heavier, than the airplane has to do something to create more lift on that side. Usually this results in the ailerons being slightly deflected, basically putting one wing at a higher AOA than the other. So when you pull hard on the elevator, that wing stalls first. Equalize the weight, and both wings track at the same AOA, allowing both wings to get to the critical AOA (or just shy of it) more consistantly, which to the pilot feels like a later stall, and my experience bears this out. Lateral ballance IS physics

Engine size will only matter if, as I said, it results in too much weight and too high of a wingloading. Lighter wingloadings mean lower AOA for level flight and less lift requirements at high rate-of-turn, so the airfoil operates at a lower AOA while making the same radius turn as a heavier plane. As a result, the lighter plane has the ability to further increase AOA, allowing more elevator devlection and a tighter turn than a heavier plane. Mass is physics, too