depends on the vane. i think the pros of more vanes is adequate steerage, with a lower profile vane, which most times will also making it quieter (depending on the vane) i don't see the benefit of 4 regular blazers vs 3, i would rather shoot 3 with more helical than 4... but i do see the benefit to 4 smaller vanes vs 3 larger (better face/cable clearance) and quieter.
6 mini blazers are way quieter than 3 full size blazers, going to a 4 vane configuration splits the difference there... not as quiet, or as low profile, but also not the hassle of putting 6 fletchings on each arrow.
i think folks should try some different configurations and decide what works best for you. if you need 4 full sized blazers, i would try to trouble shoot why, because that is a high profile loud configuration that will likely lead to face contact.