That 2 blader will penetrate better, and given the right impact direction can do a lot of damage.
But envision cutting your wrist. If you cut across the wrist you get a lot of veins and lots of bleeding, if the blade lands the other direction, and you cut the long direction of the arm/wrist, you will get very few veins and minimal bleeding.
With the arrow spinning, you have no idea what direction the blade will hit
If you can always put it thru the lungs/heart etc... it probably doesnt matter, but be honest with yourself, your not always gonna hit what you want, stuff happens.
Might as well give yourself as much chance as possible in cutting many veins to bleed the animal out. 3 or 4 blades get my vote just because of that reason.
My opinion, worth what you paid for it.