The determinant is whether the spot on the bullet where it strikes an object acts as a cam, as a hammer, or as a blade.
The curved surface of an ogive is a cam. It tends to change the course of the bullet that glances-off a surface � even a soft surface.
The flat front of a wad-cutter bullet hits like a hammer. If it hits dead-on, it tends to keep going in the same direction.
The edge where a wad-cutter's flat front meets its cylindrical shank is a blade (like a woodworker's scraper). If it digs-in, it tends to deflect less.
