I have aways shot 3 blade muzzys for everythign except turkeys. I shoot the 90 gr 4 blades with the Adder Point adapter behind it (which is 4 blade). With the 4 blade adder and broadhead it gives much more shocking power and slows the arrow down alot preventing more passthroughs on turkeys. Work great behind a field tip for rabbits, squirrels and coon too.... Really there is no differece in killing ability of the heads except like you said flight control depending on your set up and also more stopping power. I think a 3 blade muzzy would get much more penetration through ribs and shoulders cuz there essentially is 25% (1 less blade)less force neededin going through bone. Maybe it doesnt make a differnece but I think it would.... Cutting diameter is more crucial than anythign and you getthe same cutting diameter with a 4 and 3 muzzy so I've never had the desire to shoot 4s except for at turkeys.WCL