Well, I apologize for over reacting a bit there. I get so tired of these honda guys thinking naca vents are the godsend epic ram air intakes that make fast cars faster. I should have been slower to assume you were part of that group.
I still don't know if I would go so far as saying they benefit the velocity of the incoming air. They flow very little volume for their size, because they exploit the less turbulent boundary layer that sticks close to the hood. The back of a car's hood is already in a turbulent state, thus there is very little laminar, high velocity air for the naca to exploit. A similar sized "scoop" that protruded should out perform a naca vent with regards volume and velocity of the air forced into the intake. The advantage of the naca over the scoop is the naca doesnt produce flow seperation behind the scoop, a low pressure are of turbulent air. This has virtually no impact on the air flowing into the scoop.
Note the rear of the hood is nearly half the velocity of the front of the hood.
This is why engineers put these things together:
These type of intakes can exploit that high pressure, high velocity laminar air being pushed over the front edge of the hood. A Naca duct is likely no better, and I personally think it would have to be huge to compete.