..see here:
he patented 6-point Wright Drive is, in effect, a careful blending of Wright’s
12-point design with the heavy-duty gripping characteristics of a traditional
6-point wrench opening. It offers many of the same advantages of the
12-point design, including greater strength, more torque and reduced
rounding of the fastener corners. Patent No. 5,284,073.
The main advantage of the 6-pt. design is its gripping power. The Wright
Drive’s minor circle diameter, which is a measure of the ability to grip an
undersized fastener, is exactly the same as a traditional 6-point opening.
The smaller the diameter, the better the grip on undersized fasteners and
fasteners with badly rounded corners.