Five-seven only really sucks in civilian loads, where they chop a whole thousand FPS off the potential. Well, ok, it sucks as a "sporting cartridge" in general since the energy it carries out of the P90 (much higher than from the FiveseveN pistol) is really not enough to reliably stop anything that won't instinctively fall down when shot (see: people).
That said, if you chop 1000FPS off a 9mm, you end up with a paintball gun shooting ball bearings, and if you chop 1000FPS off the venerable .45 ACP, the bullet somehow has magical negative velocity and will come out the wrong end of the gun or something.