There is no doubt that this loading has proven to be among the best, but when you actually chronograph these loads in real guns, not test barrels, you usually come up velocities in the 1250-1300 fps range. These numbers are my guns my loads my Chronograph
Yet the many of the same people will tell you that a 124 gr +P 9mm bullet at a chronographed 1250 fps is totally inadequate. Those are real numbers you will get from real guns, not some numbers published in a ballistics chart.
The truth is that any of the common rounds, 9mm, 357 mag and 357 Sig, as well as 45, and 40 are all pretty much equal in terms of effectiveness when the best loads are chosen for the individual gun.
As a SD round a 357 mag works, but has several huge disadvantages. Much more muzzle blast and recoil, considerable loss of velocity when used in barrels shorter than 6", and very limited ammo capacity. They are at their best when loaded with heavier bullets and with longer barrels and used for hunting or long range shooting. A 357 mag with a barrel shorter than 4", and loaded with 125 gr bullets is pretty useless in my opinion because you get all of the disadvantages magnified, and with LESS velocity than from a 9mm pistol.
