If the .357 SIG had hit the market at the time LE agencies were getting dissatisfied with the 9mm, there would almost certainly never have been a .40 S&W. The .357 SIG is a excellent round. Its greatest problem is the lack of readily available cheap practice ammo as well as being chambered in a limited number of pistols. For many shooters, the fact that it is a bottleneck round makes it much less attractive for reloading as it precludes use of carbide dies. It is very limited in available and usable bullet weights. If it could handle a heavier bullet, it would be better. The .40 S&W does offer advantages for those who want a larger bore using heavier bullets. With lighter weight bullets, the .40 offers lots of velocity and on target energy. Yesterday I was in Wal-Mart. They had lots of .38 Special, 9mm, .40 S&W and .45 ACP. They had one box of .357 Sig. ammo... WWB at $29/50 rds. By contrast, WWB .45ACP is $35.97/100 rds and .40 S&W 180gr. FMJ are $29/100 rds. For the normal shooter who does not go through a wheelbarrow load of ammo every month, who tends to go to places like Wal-Mart and buy a box of ammo to shoot, the prices cited are a big reason why the .357 SIG is not making much progress in the market place. It is likely going to wind up like the .280 Remington... fine round but now largely only used by those who just like something "different." Everyone else just buys a .270 Winchester. JMHO.
"People should not be afraid of their governments. Governments should be afraid of their people."