I wouldn't get too hyped up on thinking that a sectional density of roughly .140 and 1400 fps (now you bump it up to 1500 fps) is necessary shock and stop someone nor a bullet having to remain above the sound barrier while inside the person. By nature, such stats would always benefit the smaller calibers because the bullets can be lighter while retaining a certain sectional density. A .40 cal 135gr @ 1500 fps vs. a .355 125gr @ 1500...who really cares, both will be more than lethal. The Sig is going to be a little better breaking through hard objects and will penetrate a little deeper, but of those two, the 135gr is likely to open more violently, doing more damage. Sectional density is a factor, but it's not the only factor in performance.