I am of the opinion that the small diameter will pay off well in penetration. Check out Dr. Ed Ashby's research in Africa on arrow penetration. He found that the shaft drag wasa huge factor. His "shaft drag factor" was used to reduce the penetration potential of an arrow/broadhead combination based on his thousands of shots into African game. His research showed that the arrow smaller than the broadhead ferrule was the best penetration, arrow same size as ferrule was 90% as good, and arrow larger than ferrule was only 60%.