As a bullet maker (118gr. 30cal.), these guy's that sort bullets don't have a clue. I would sort them by color. What an absurd waste of time, bullet sorters need to spend more time at the range seeing what all that sorting looks like on the target. I wonder how many of the basic bullet sorters has a scale that is of sufficient quality (huge cost) to measure accurately bullets to the tenth grain.
To answer your question, if you feel a need to measure bullets, checking the base to ogive would be the most valuable. It is more important to keep a consistant base to ogive dimension than having bullets .2gr difference in weight.
Why, because differing ogive lengths changes the bullets dimensions, hence accuracy. That being said, you have to be very consistant in your technique of measurement.