"In my experience", I tried single bevel broadheads in 2015. I learned how to sharpen them in the Spring time and started practicing after work on a daily basis. I was truly amazed how accurate they was. Fast forward to opening day here in Iowa. I decided to take a big mature doe as she made her way towards me. She came completely broadside at 12 yards, I drew back, hit my anchor, picked a spot and released. My arrow hit exactly where I was aiming. I watched the doe take a few leaps and bounds, then walk off as if nothing. I watched her through my binos make her way down to the creek bottom and lay down. I sat there watching her for about 10-12 minutes before I lost sight of her. I got down after a hour and made my way to my arrow that was stuck in the ground covered in blood. I was curious about what kind of blood trail would await me as I started making my way in the direction the doe took. And besides at the point of impact, I could not find a spec of blood to save my life! I really searched. I found her prints but no blood. I made my way to where I seen her bed down, and there I seen a small amount of blood but not her. I went down across the creek and found her up on the other side piled up about 90-100 yards away from where I shot her. I was really careful when I was gutting her because I wanted to check out what the damage the single bevel broadhead has done. there was plenty of blood in the chest cavity. I went through both lungs just behind the heart but there was no "S" wound channeling like I heard so much about.
About a week later, I arrowed a heavy antler ten pointer that I never recovered due to the lack of blood on the ground. I hit him quartering away from a deer stand that was 14 feet off the ground. found my arrow about 20 yards from where I shot him, covered in blood. I found very very little blood out to about 150 yards to where it trickled off. I took off a day of work and really looked along with several friends without luck.
After that experience, I went back to my Zwickey Deltas. The very next buck I shot was a eight pointer that field dressed out at 235lbs. Shot him at 18 yards and he only made it about 28-30 yards before dropping. The blood trail was unreal. So for me, the single bevel is only a gimmick. I will never use them again. I shoot the biggest broadhead Zwickey offers. Keep it simple, bigger the hole, the more blood on the ground.