BennyS, I don't consider it a waste of time.

I resize all handgun cases, general after or before resizing, it makes no difference. It removes the sharp edge and helps prevent lead/copper shaving when seating the bullet. After they been flared, it will be harder to get a good chamfer in the mouth edges.

Chamfering also helps remove tiny nicks and such that can lead to mouth cracks. Ask any good machinist why they chamfer holes after they've been drilled. Ever seen cracks extending from one rivet to another? And where do the majority of cases crack? From the mouth down.