Rangeball. Ditto what C903 stated.
I do use Mechanical heads for Turkey hunting but that is because with all things being equal: Mechanical heads use part of the KE to open/expand and therefore, shot from the same bow will not penatrate as well as fixed. They stay in the bird where my fixed will zip through like paper. Now you could debate the various types of fixed vs each other and so on and so forth but that' s not my point here.

What Im saying is that if I shoot any fixed blade equally as well as I do anyone head (and I do) I will choose that head over the others for the reasons stated by C903.
Now if a person has greater accuracy with mechanicals to the point of a serious difference use what is best for you and your set up.
My 125 Thunderheads, 3 blade fix hit the same point as my field points. I get much better penetration with my fixed blades. It works for me, an enterance hole and an exit hole with my fixed vs just an entrance hole with mechanicals.