Okay, I'm fairly new to traditional archery but I'll add my 2 cents. I've probably shot 50-60 deer total and about 1/2-1/3 of those were with a compound bow. I've had deer with heart/lung shots bleed like crazy, and others that sealed up. I've had pass through on all of my deer. Unless you are using a very light bow or hit the shoulder square on you should have a pass through. This doesn't always translate into a good blood trail. High shots will bleed, not because of positive pressure (Sorry Charlie, just not true), but because blood vessels that feed the intercostal muscles and other small vessels are cut. Sometimes that is all you get. I shot a deer with a 7mm mag through the heart that had a little blood at the site of impact and then nothing, I mean nothing, between it and the carcass that was 45 yards away. It's not an exact science. Alot of it depends on how fast the animal is moving after the shot. The more surface area of the blade you use the more likely it is to cut vessels and vital organs, the more the animal bleeds. Usually this will translate into a better blood trail, but not always. Obviously if the arow doesn't completely penetrate it will not cut as much tissue so having more blades in this circumstance will not help. Usually this is not the case with deer. Since I am new to the game I plan on using 2-blades for hunting because eventually I want to hunt hogs. 3 blade or 4 blade setups would probably work better as far as blood trails go, but when I eventually go hog hunting I want to give myself the best opportunity for penetration. As far as deer hunting goes I will probably use the two blades as well, but that is really without any good justification other that that is what I have and I think it will do the job just fine.