I never worry about the size of the pan, but then I usually only bake quick-rising breads. Surely 8 versus 9 inches shouldn't make a difference. A tall, rectangular loaf pan is certainly not the same as a low, square one, but I've always had the same results for quick breads. Recently I made a zucchini chocolate bread that didn't turn out more like a brownie than a quick-bread, although it was delicious. The bread/brownie was equally over-moist in both types of pans.