Ben, Even though I don't use them I think a Big nasty Mechanical would be Great on turkeys. I've killed all my Bow killed Turkeys with some model of Slick Trick.
The only head I don't like that is actually touted as a Gobbler head is the NAP Gobbler Getter. I think the rounded head is too prone to skipping off if you have a steep angle. A layer of feathers is tougher than you think. I know there are guys that use them and swear by them, but I also know several that have had less than ideal results. Anyone that shoots them should be aware of the angle.
I have also tested some of the giant cut heads, Magnus Bullhead, etc. but was never able to get the flight and accuracy I demand and expect out to 30 yards.
I may load up some Spitfire XP's this spring when I head to KS. I think the Synper that Rob uses would be a good choice also. Any head that is sturdy, cuts a good hole, and flies well will work.
As in Hunting anyGame there is No substitute for a well placed shot
Dan