Here's an interesting,scientifically compiledread:
http://www.tradgang.com/ashby/
Check out the study on broadhead performance. While the testing did not include mechanical broadheads, 2,3,4,5, and 6 blade broadheads were compared/tested on a variety of game animals.
Dr.Ashby was shooting a 90# longbow, and his partner in the research was shooting a 85# compound so, I doubt that KE was an issue.
This may change your opinion of 2 blade broadheads.
As far as bloodtrails, there are three contributing factors:
1) Shot placement,
2) The presance or absence of an exit wound,
3) The SHARPNESS of the broadhead.
I have hunted with 2, 3, and 4 blade broadheads over the years. I started out with the 3 and4 blade heads, thenswitched to 2 blades after a local proshop owner had me shoot a few. I have never looked back. Silent flight, superior flight characteristics,unequalledpenitration, and morbid bloodtrails. In tweny years of hunting and around 40 kills, I have neverexperienced a "wound slit" closing up, evenwith marginalhits.If you make a good shotwith an exit wound but, get little orno bloodtrail, then your broadhead was not sharp enough.
"Consensus is the absence of leadership"