I have a number of Forstner bits made by various manufacturers. And I've noticed
that some of the bits tend to clog with wood chips more than others do, especially
in the larger sizes. This is annoying because you have to stop the drill and clean
out the bit.
When I started comparing the bits, I discovered that the "mouth" of the bits weren't
all the same. On the bits that clogged, the sides of the mouth were nearly parallel.
On the other bits, the mouth tapered out toward the top to eject the chips cleanly.