I like longslide 1911's, always have, always will and always will have had at least one. The best reason to have one is you WANT one!
But, forget longslide performance... at least back burner it as an unexpected bonus if you find a powder that you chrono and squeeze a dozen or more FPS out of it over a 5" barrel.
Longslides for sure add sight radius, and weight forward that helps keep recoil down as well as add a bit of stability, and they (IMO) look great.
Also in a higher performance cartridge that was designed for short barrel like the .357 Sig, the ball of fire out of the muzzle virtually disappears and the sheer blast volume is directed more down range... perhaps adding to the discomfort of shooters in adjacent lanes
OP, maybe you can get a 6" slide and 6+" threaded barrel... get a screw on comp and see how you like it? It'll be more easily found and maybe even cheaper.