Most important thing about crimping...is to crimp in a separate step. Do not crimp as you seat! A spacer washer under your die as you seat makes this job really easy.

Heavy vs. Light is the most used crimp terminology.

A 357 bullet doesn't really need much crimp because the bullet is so light.

Case neck tension is a powerful part of a crimp. So if you apply a roll crimp really heavy you will buckle your shell slightly and reduce the neck tension...this is hard on brass and seriously reduces your crimps holding power. This is greatly amplified if you seat as you crimp because the seating stem continues to seat as the crimp is being formed.

Keep in mind that if you over-crimp "some" jacketed bullets..you can mis-shape your bullet and compromise the jackets integrity.