I haven't got into one of these theads for a while and I've got the itch, so here's my 2 cents from over 20 years of bowhunting.
I've shot a pile of different heads over the years, most of them have got the job done. Never shot a mechanical head for a few reasons, number one is I'm very conservative with my equipement. The least amount of nuts, bolts and mechanical items means fewer things go wrong IMO.
I truely believe shot placement is #1 above all factors, the most important.
The other factors I place of equal importance.
Heads must be scary sharp (of surgical nature) which I'm not convinced all the heads on the market are as sharp as they should be.
A low angle blade design is very important as it prevents deflections from bone impacts and improves complete arrow penetration. When I say complete penetration, I mean the arrow passes completely through and does not stay in the animal. From my experience an animal which is not carrying an arrow bleeds better and doesn't run typically as far after the shot.
A broadhead that offers a high ability of complete penetration also provides a higher percentage of maximum wound channels. Consistently producing 2 unplugged drain holes is what drastically increases animal recovery.
A steep angle blade design like you see on most of the expandables can easily change the intended path of the arrow through the animal and limit penetration, especially when hitting bone.
Low angle blade designs provide excellent flight capabilities which promote accuracy and penetration.
A 3:1 blade angle is ideal. The Woodsman / VPA designs are a perfect example of a tough head with all those qualities. I have been fortunate to shoot a lot of deer with those heads and have never lost an animal while using those style heads. I've shot a pile different heads over the years in about every blade configuration and style made, none have given me as consistent results as that 3:1 3 blade design.
So, that's my 2 cents. I'm sure some will dissagree....but all I can tell you is my experiences. When those heads are parked on the front of my arrow I have absolutely no doubts in them......none.