One of the major gripes about mechanicals when they first came out, was the trasfer of energy to the head in order to make the blades come out. This resulted in fewer pass through shots on deer which didn't make many bow hunters happy about using them with deer. They do work, though, and have come a long way in the past couple of years. Some companies have made pass through shots with mechanicals a very easy thing to achieve.

However, the general rule of thumb on turkeys is the need for the arrow to hit home and stay in the turkey. One of the best shots on a turkey is right through the vitals from the side, which essentially pins the turkeys wing to his body making it impossible for him to fly. They can still run.....but not if you hit them square. So the mechanical broadhead was the best choice because of it's tendancy to stay in game and not achieve a full pass through.

That's the way it was explained to me.