After talking to a guy who was telling me that having exact same trim lengths was very important I went out and tested it (not extensive- but enough for my purpose). He said that you would get different bullet seating pressure and different velocities due to different grip on the bullet. Using a bullet seating gauge and then shooting over a chronograph with cases that were exactly the same vs those with some variations (still within min and max) I could never see a repeatable difference.

If you are putting a role crimp on then it is important to be the exact same- but not many people seem to be using a role crimp anymore.