First off, what have you been using . . . and why do you want to change?

I've been thinking about going to a two blade like the Stingers only because I've heard they shoot closer to your field points than 3 or 4 blades. BUT! My bow guru indicates the 2 blade has it's own set of tuning problems. It's been my experience that the 2 blade penetrates deeper than a 3 or 4 shot from the exact same bow. But the 3 blade provides better "arrow" dynamics when lined up with your fletches.
I also used the NAP Spitfire mechanicals. They shot noticbly closer to the field points, but I never recovered anything I shot! I hunt Elk, Mulies, large animals. So I gave them away.
I wonder if there is an in depth study done somewhere on the internet?