I hear that the three blade doesn't always open up on impact. And the two blades I never heard any problems with opening on impact. Just make sure he stays away from bone, (easier said then done). If he is starting out I would go with a fixed blade then he doesn't have to worry about the blades deploying in the quiver or when drawing back, There is a shock absorber on both that holds the blades in place, if he is missing one they don't fly correct.