Underwoods has a 135gr .40 claiming 1500 fps, which is good I guess, but the poor sectional density is going to make for shallow(er) penetration compared to a 125gr .355" (or .357"). Given similar bullet weight, in this case 125gr .355" and a 135gr .400", in terms of sheer velocity the .40 will push a 135gr faster than a 357 Sig will push a 125gr. But again, sectional density advantage goes to the 125gr.
Fast is good to a point, and that point being whether the bullet can handle it or not. If not, there's not much point to pushing faster. From a 6" Glock 24 I've loaded 135gr Nosler to 1,850 fps average using Longshot...but it's useless. Fun, but useless.
Glocks and Single Actions