Screws or shafts

I am building a tower for my new robot and I am wondering if there are any advantages to using screws over shafts on your driven gear?

It’s usually screws in combination with bearing flats, as the circular screw and circular hole mean less slack in the joint. Make sure to use a nylon locknut tightened appropriately to reduce friction.

If the joint is too large, shafts work perfectly fine as well.