Seems the curved shaft get caught up more in constructions, where the straight (geared) reaches better under shrubs fences etc....pretty sure all the "pro" trimmers are geared.
Can't say I've ever thought of the direction, others then to make sure I put the blade on correctly
Still, if the preference is reversing rotation this is how.
I have both, it kinda doesn't matter if it cuts well.
I have seen others somehow unable to adapt mostly to lower power homeowner grade tools that have a loud opinion. Reality is both work. Geared lasts longer.