[sammyg2]

If the bolt or nut is a standard hex, a 6 point socket will get a better grip and transfer more torque than a 12 point, especially if the head is rusted or partially stripped or whatever. The 12 point is more convenient as it can go on indexed many different ways.

Iffn the head is made for a 12 point (as in many aircraft fasteners or some header bolts) then you have to use a 12 point.

I prefer 12 point on smaller sizes, like 1/4" drive and smaller 3/8" drive.
For the larger 3/8" drive sockets and all 1/2" and 3/4" drive, 6 point is the way to go.

And all sockets that will be used on an impact gun should be 6 point, hardened, heavy duty and designed for impacts or they'll eventually crack and can cause injury.