My opinion, zwickey, magnus,STOS. Simple, fairly inexpensive, easy to resharpen,not assembled..one piece design, I think two blades are by far the best design in the world (thats gonna get me some crap) Less chance of hanging up on anything, fly great when matched properly, penetration can't be beat by any other head with more surface area (more blades). Thats science, not my opinion, less friction. Don't give me a hard time for that comment, argue with a physics professor. There are I'm sure plenty of other two blades out there, I've just never had any reason to go to them. These three have killed every animal I've taken from beaver to bison. I'm sure others have never tried these three for the same reasons.
You'll find your favorite and swear by them one day!