9mm is worth sorting. I'm relatively new to loading 9's, so I'm still in denial about it. (Meaning, I DON'T sort by headstamp - yet.)
Most experienced loaders already know this, but for the rookies: It's good to sort by headstamp because of the differences in cartridge internal volume. Now (I believe) it's not that critical for most calibers; but in the case of 9mm, it probably is. The cartridge is so small, that minor differences in volume and mean big differences in pressure - with the same load recipe.
My hottest 9mm load is 6.1g AA5 w/ 124gJHP; and the headstamp doesn't seem to matter. And the chronograph doesn't show any unusual velocity fluctuations. Of course, I didn't check the headstamps - they could have all been the same
At any rate, I don't sort. And my two 9mm guns gobble up and spit out everything I feed them without any problems. So I have found no need to dig into that logistical nightmare of sorting.