Hold on...
Smith brought back the 640/Centennial/340 series because of one or two magazine articles...
Seriously...It happened...
That little handgun is the best deep-cover concealed carry gun out there...It's also become one of their best sellers -- and it was "dead" before the articles.
The 940 in 9mm is more efficient in reloading all around than the 640/340s in .357...
A 9mm in moonclips can be reloaded if you're injured and flat on your back. A regular 640 can't -- as easily -- straight up and down using speedloaders. (Speedloaders don't do well vertically inverted...
)
Plus, with newer loadings, the 9mm -- especially if it will shoot the "longer" 9mms also -- is more efficient in a short barreled handgun than a .357 is -- because the .357 loses so much velocity (to my understanding)...
A 940 in 9mm is probably better against human attackers; the 640 in .357 is probably better against animals -- at least according to Chuck Karwan...
My concern would be to have a 9mm that would hand ALL types of 9mms -- even the "longer" calibers...
(I'm not that familiar with 9mms -- but isn't there a 9x21 and a 9x23? Greater case capacity would be a desirable thing -- as long as it didn't create head-spacing problems, right?)
Isn't a 9x19 the "regular" 9mm parabellum? It would seem extra case capacity could be used to advantage...