I like the keltec for the fold up small storage capability while still having better ballistics than my pistol due to 16” barrel. While I agree an ar9 platform would be better ergos and easier to add sights. I think if I were to have to carry/store a full size ar9 with 16” barrel (ie. a full size rifle) it might as well be in a rifle caliber. I think the sub 2000 fills an in between role. Its better than a pistol but not as good as a rifle.