Is there any advantage to resting (banana) bread batter?
The leavening action of baking soda begins as soon as it is moistened - that is as soon as you mix your wet and dry ingredients your baking soda begins the chemical reaction that creates the carbon dioxide which causes the rise in your quick bread. Because of this I would say that there is no advantage, but in fact a disadvantage to resting a quick bread. Also, it is usually recommended to mix quick breads as little as possible and over mixing them can cause them to be tough.