we use elmer expandables for elk hunting because shoots are long and more poundage does help 65 lbs and 75 lbs. now for whitetail deer hunting I only shoot nicer bucks now days I use a completely different set-up I shoot 55 lbs. with a 125 gr. hand sharpened broadhead called a Zwickey Eskimo 2 blade with bleeders, the reason bow shots are close 20-25 yards and these cut on contact hand sharpened broadheads cut more,draw more blood to follow blood trail and many times kills the buck faster as it does on pigs and bears too. most bowhunters do not have the skill to sharpen fixed blade broadheads properly but could learn if they wanted too. also in order to make a fixed blade broadhead arrow to fly accurate you need to shoot less bow pounds maybe 55 pounds or less ? Zwickey broadheads are one of the oldest broadheads made and to be honest Fred Bear used Zwickey Broadheads before he made the famous Bear head,Zwickey still makes Broadheads in the Twin cities of Minnesota.i have bowhunted since the mid 60`s before the compound bow was invented, so I have seen it all and still believe those old Zwickey broadheads kill better.
Its easy to sharpen Zwickeys.
I'd have never known you couldn't shoot heavy draw weights with them. We shot up to about 72 or so pounds quite often, and the accuracy of them was good enough for much longer shots than we should be trying anyway.
As to killing better, I can't see that at all. You have X amount of cutting edge, and diameter. Given same sharpness and penetration depth thats good enough, then all will be equal.
COC will give better penetration than any other head is about the only difference we could ever see for sure.
On teh low end, the wife shot eskimo 110s out of a 45 pound bow and had the tip of the head sticking out the other side of a pig with 3 inch thick shields that bottomed out a 350 pound scale.... so I know they also shoot at low poundage for sure.