RE: Fixed or mechanical broadheads
For me, I take into concideration the animal I'm hunting and the most likely shot distance that I may enounter on that animal.
For instance, when I am planning on hunting turkey, obviously the animal is small and penetration won't be an issue with a large cutting mech. out of MY bow, and I want a lot of cut on the way through the animal.
When I hunt antelope, again a small animal, BUT my shot may be on the long side, so I stick with a fixed blade because I expect my arrow to be loosing KE at longer distances.
On whitetail, I fully expect my shot to be maybe 25 yards, so I think either head would give me plenty of penetration, BUT if I oops and hit the shoulder, I want the fixed, so that's what I choose, although I've shot several with expandables with no problems.
On elk, they are big bodied critters AND my shot may be longer, so I want all the penetration I can get, so I go with fixed!
So that's how I decide.