Mike,

The reason a lower let off bow can generate more energy is because of its effect on the draw force curve. Since you are holding more poundage at full draw the arrow will reach peak poundage quicker and for a longer time through the curve. The higher let off starts out at a lower poundage and takes a fraction of a second longer to reach peak weight.

I agree with moonge and RN,HUNTER that the increase in power is minimal at best because of the advance in cam design and the incredibly steep draw force curve found in today’s bows