I think after talking to enough people with experience in the field and seeing a few gunshots (on video admittedly) I'm pretty convinced the part about a pressure wave killing instantly by "shocking" the brain or what not is indeed a myth, especially at handgun velocities.
However, I'm also nearly convinced that a bigger secondary cavity caused from the pressure wave can in some cases cause enough additional trauma to speed incapacitation. I've seen a video of a 30-06 rifle not only explode the ballistics gel into smithereens, but it also broke the table in half!
Borris once told me he didn't trust 115grain +p ammo, because he'd had problems with it reaching the CNS on some larger animals, yet at the same time he noted it had some very impressive entrance wounds. And that tells me the entire story right there... you simply MUST have good penetration, but if you can find a bullet that can give you both good penetration and explosive cavity wounds, go for it! That's why I think .357 does so well. It gets the penetration needed but has that extra edge of velocity to tear #$IT up on it's way in.
Just my humble opinion.