When I first started shooting the GK Silverflame heads, all they had was 1 1/8" wide heads. I loved the looks and flight of these heads. I proceeded to kill several nice critters with these heads. Two particular deer made me almost go to something else. I shot two nice deer in one season and made textbook shots on both bucks. When I went to trail these deer, I had nearly no blood on the ground. In both cases, the deer only made it 40-50yds and I found both. After confirming that the shots were as good as I thought they were, I could not believe that the blood trails were as bad as they were.
I emailed GK and asked Marcus if they made a wider head because I was concerned about the lack of a good blood trail. That was right when they came out with the XL (1.5" wide). He sent me a pack to try out.
I have not kept any scientific records, but I can tell you that the extra 3/8" makes a huge difference. The blood trails with the XL's are consistently better than with the standard 1 1/8" model.
I still have and use both size heads. I use the wider heads for deer, small pigs, and any critters in that class. I use the narrow heads for large pigs or tough critters that I might worry about penetration with.
I really think a guy should shoot the most draw weight he can shoot well, with the widest head he can consistently get entry AND exit holes with.
Bisch