The design of the iron, specifically the loft of the iron, is the major factor in trajectory. CG is a lesser factor in trajectory, but is a factor. Shaft type, flex, design is a lesser factor as well. The shafts effect will be seen more in comparing extremes, like a A flex to an X flex, but less of a factor comparing an R flex to an S flex, for example. A 1 or 2 degree loft difference should be seen more easily.