gunfan:
If I knew I was going to be in the situation your described, I'd want the biggest, meanest handgun (or shotgun) on the block, preferably mounted on wheels…
However if I was limited to a middle-bore, 5-shot snubby – then yes, a 9mm Para. would be as acceptable as say a .38 Special.
But if I could get a more compact S&W I-frame, or Colt Pocket Positive sized gun with a short 1.250” cylinder and equally sized down frame I would choose the more powerful .38 Super over the lesser 9mm Para in the same package.
The .38 Super cartridge is the longest, popular round that you can get into a short 1.250” cylinder, and anything the 9mm can do, the .38 Super can do better. Other then the 9mm’s international availability and relatively low cost for practice ammunition I don’t see any advantage in using it in place of the .38 Super.
I see this concept as a pocket or ankle holster gun – or one carried in deep concealment. In such an environment anything that shortens the overall length or reduces weight or bulk is advantageous.
Most of our traditional revolver cartridges are based on black powder beginnings, and therefore long in length. Or they are Magnums, made even longer to prevent use in non-magnum guns. All of this requires long cylinders. Pistol cartridges were made to be used with smokeless powder from git-go, and are shorter. Unless someone is going to bring out a new line of short revolver cartridges (which is unlikely, Federal tried with the 9mm and failed) pistol cartridges will be the best candidates for use in a short cylindered revolver, excluding the .32 H&R Magnum or various .22 rimfires. The .38 Super by the way is the same OAL as the .32 S&W Long.
An argument could be made to shorten both the frame and cylinder to match the 9mm cartridge, and that could have some merit. But if we are going to look at a duplication of the S&W I-frame/Colt Pocket Positive/Taurus I.B. with a 1.25” cylinder I’d still advocate the .38 Super over the 9mm.