From 1929 till the development of the 10mm the Super was considered by many to be the most powerful round that could be fired out of a semi. It's velocity and ft. pds. of energy produced at the muzzle were the primary factors which folks looked at when figuring it as more powerful than the .45 acp. Not to mention more powerful than the 9mm.
For the last 25 or so years there have been 3 rounds which have received unprecedented attention from ammo manufacturers and have improved their ballistic performance greatly. These are the 9mm, the 40S&W and the .45 acp. The .38 Super has not received as much attention, unfortunately.
The 9mm is a much better round than it was 20 years ago. But even in it's best loadings, where it is operating at it's peak pressures, the Super can still beat it by 100 fps or so and can do this without reaching peak pressures. For some shooters though the extra punch may not be worth it.
The 9x23 uses a case which has the same external dimensions as the Super. It can operate at higher pressures than the Super though because internally the bottom of the case is stronger and thicker than that of the Super. It actually holds less powder than the case for the Super can but because the case is stronger can produce higher pressures and thus velocities. For example Winchester produces a load with a 125 gr. Silvertip that gets 1450 fps and 583 ft.pds of energy at the muzzle. This is more than any load for the Super that they produce and the 9x23 handloaded can get more.
Yes you can shoot the 9x23 from a 38 Super barrel. A heavier recoil spring will be called for and, if you plan on shooting a lot, maybe a heavier mainspring as well. Barrels for the 9x23 tend to have a shorter life than barrels for the Super though. So I'd shoot it through a dedicated barrel myself.
Now on the 40 S&W lets look at two loads from CorBon:
CorBon offer a 40 S&W load with a 135 gr. bullet at 1325 fps for 526 ft.pds. of energy.
CorBon offers also a good load for the Super of a 125 gr. bullet at 1325 fps and 487 ft pds of energy.
With a heavier and slightly larger bullet the 40 generates as much velocity and more energy. With a 165 gr. bullet CorBon, Remington and Winchester offer loads for the 40 that generate around 480 ft. pds. of energy at about1150 fps.
So if a fella has a 40 S&W he or she may not see the "need" for the Super as it don't give them anything they all ready can't get ballistically.
The 45acp has received alot of development the last few years I'll use CorBon loads as an example again just to keep things even. They offer a 165 gr. load for the 45acp at 1250 fps and 573 ft pds of energy which beats both the above mentioned loads.
Now we could play around with various weight bullets and loads, velocities and energy figures, look at the 357 Sig vs. the Super or the 9x23, argue if 50 ft. per second makes a big difference or 20 grs. makes a big difference but the point is that you don't really ballistically get something from the Super that a person can't get elsewhere. Choices are good.
So what do you get?
You get a round with an interesting history. A round that has been chambered in some of the best handguns ever made. A round that gives you more than the 9mm does. A round that can give you a gun as effective as the .357 Mag in many of it's defensive loadings with more rounds on tap and faster reloads. A round that is easier to reload than a bottlenecked case. A round that can use most any 9mm or 38 caliber bullet giving you many choices if you reload. And a round that has a growing number of good commercial loads available for it. A very good round one I prefer over the 40 S&W, over the 9mm and certainly over the .357 Sig.
A friend and I worked up a load for it a few years back with a 148 gr. semi jacketed lhp bullet at 1300 fps which was a very good deer load.
I like the Super cuz I like it. To me it is one of the best rounds available. Comfortable to shoot.
tipoc