Cabinet screw drivers and bits for slotted screw heads have parallel flats
on the blades and the tip is the same width as the shaft diameter.
Gunsmiths' screw driver bits are made in this pattern. Blade tips may be
ground to fit the screw.
Phillips PoziDriv has parallel faces on the tip. They work best with
PoziDriv screws but usually work well with normal Phillips screws.
All the square driver bits I have are tapered on the sides of the square,
as are the square recesses in the screws. They don't cam out nearly as
easily as a normal Phillips bit in a normal Phillips screw.
Phillips-type drywall screwdriver bits have parallel faces and serrations
to reduce camming-out.
Torx (star drive) is the all-around best. The drivers do not cam out and
require little pressure to keep the bit engaged in the screw recess.
Unfortunately star drive screws are not as readily available in different
sizes and lengths as square drive.
Many RVs and mobiles used to have butterfly screws. The recess resembled a
bow tie. The screws were often damaged by using a flat bit in the recess.
It worked - sort of - but was prone to slipping and stripping.
For the types and sizes needed in RVs the square drive is probably the best
all around.
Al