Bullets kill by hydrolic shock. They kill by massive hemraging that is induced my magnum doses of KE. The massive shock makes the vitals "explode" and kill the game quickly.

Broadhead DO NOT kill by hydrolic shock, or magnum doses of KE. They kill by hemraging but not in the same way as bullets. The broadhead cuts through vessels, viens and arteries. This causes the blood to pour out and the game dies quickly by blood loss.
You NEED sharp broadheads so they will cut these life lines and make the game hemrage. If the blades are dull, the arteries will literally slide around the blades and not be cut. This will equal less blood for tracking and lost deer do to seemingly well hit deer not bleeding enough.
A good example of how this works is by running the blades over a rubber band. Sharp blades will easily cut through the band (artery) and cause blood loss. The dull blades however will just slide around the band (artery) and won't cut it...less blood loss.

A real life example is like a person being shot through the chest with a 20mm tank round. Massive shock. However a person will die just as fast if the main arteries in your thigh, or armpit are cut by a knife. The blood will pump out and kill the individual just as fast. Sharp Broadheads
--If the knife isn't sharp, it won't cut and the wound will be superficial.

**Sorry I know its rough, but I tried to get the main point across quickly so I can continue packing for tomorrow, but I feltI needed to express my opinion on this.**