IMHO, I agree with the basic premise of your question...i.e. a longer barrel gives you straighter trajectory. BUT adding a "Suppressor" doesn't necessarily complete the rest of the premise...shoot as straight as a 16" barrel alone. My reasoning lies in the changes in barrel pressure (and barrel Harmonics) created by a Suppressor. And my thought lies in my experiences in shooting and reloading Long Guns where my three to five shot groupings opened up some (regardless of the bullet weight changes tested) once a Suppressor was added to the barrel, thereby changing the Harmonics of the barrel. So to bring the groups back -closer together- I had to change bullet weight, seating depth and even powders until I found the combo that the barrel-with Suppressor, liked the best and produced the best results. So getting back to your question, I would submit the best way to find the answer to your question, TEST different loads and see how the two combinations compare in the end. Now I will admit that my experiences are based on Long Guns and shooting from 50 yds to 600 yds, some of which was in competition. And therefore my handgun experiences lie in max 25 yard handgun target and combat experience in accuracy and grouping. But I do find you pose some interesting questions and I'd love to see what you come up with in the end.
