At rest they will allow heat to escape out of the hood, and at speed they should allow a bit of air to flow into the engine bay (assuming the car doesn't have a proper under tray or otherwise sealed engine bay). Those holes are relying on positive pressure on the hood to force air through them at speed. There isn't much positive pressure there at speed to take advantage of.
A NACA duct would force more air through at speed, and possibly cause less drag. They do not rely on positive pressure to force air. They rely on passing air and a tumbling effect produced when the passing laminar air encounters a sharp cliff and goes turbulent. There is a lot of passing laminar air going over the hood to take advantage of.
A full on scoop would force even more air in, with the obvious huge penalty in drag associated with scoops. Scoops rely on passing air as well, not requiring high pressure zones.