-MIKE- wrote in :

I guess I don't understand what all the hubbub is about.
Perhaps the metal is stronger, thus the smaller diameter.

If there's sideways loading on the screw, you want the shank
to bear against the sides of the hole. You don't want all
the load to be carried by the screwhead bearing on the
countersink.

If the screw is purely in tension, then it doesn't make any
difference (as long as the strength of the shank is still
adequate).

Granted, for most any application where you did have a
sideways load you wouldn't use a Home Depot grade screw
anyway (and it would likely be stainless or silicon bronze,
not a common galvanized screw).

John