I guess they just want less recoil.
Most competitive target shooters I know use 45's but also reload, To get lower recoil they just tone their loads down a bit with lighter bullets and smaller powder charges, The guys out there using 38 supers and 9mm's more then likely dont roll their own ammo. If you dont reload or dont ever want to reload Id say go with a 38 super, But if you are dead set on a 40 smith then deffinately get a 1911 frame. I'm with new guy when i think of a 1911, 45 acp comes to mind and a 1911 in other calibers i feel defeats the purpose too. But to each his own.