Some good info by CarteachO

Despite the staggering number of choices amongst semi-auto pistols for personal protection, there are still a large segment of the population who prefer revolvers.  Even those who swear by one auto or another often have a small revolver as a backup.
Why?  Because they work.  It’s not new technology.  Most are not fancy.  Almost none have any kind of external safety to remember under stress.  They just….. work.  Pick up a double action revolver, squeeze the trigger, and if it’s loaded there will likely be a Bang.  If not, squeeze the trigger again and try the next hole.

Revolvers have been around the personal defense scene for many generations, and for concealed carry, the shooting public seem to have settled on the snub-nose for everyday carry.  Short, small, relatively light, and utterly dependable, a snub nose has been in the pocket or holster of many an officer or shopkeeper since the 1940’s.  Even earlier, lawmen were cutting down larger pistols and making their own snubbies, the easier to pack some protection as they patrolled city streets.  J. Edgar Hoover required his agents to be armed at all times, and demonstrate proficiency with the little snubby on a regular basis.
There’s a wide range of caliber choices for those packing a wheel gun, but two still hold the position of top dogs by a very wide margin.  The .38 Special, a round that’s been chambered in pistols since 1900, and has been in wide use since the 1930’s.  The other, the .357 magnum, developed from a desire for a more powerful version of the .38 special, and that’s exactly what it is.
Dimensionally almost exactly the same as the .38, the .357 is made just a little longer so it will not chamber in a .38 Special hand gun.  This prevents the high pressure .357 round from being mistakenly fired from a .38 special gun…. and also gives us a wonderful choice.  This closeness in dimensions means any firearm chambered in .357 will also shoot the .38 Special, allowing the shooter to have a much cheaper, quieter, and gentler round to practice with and enjoy.  While point of impact will change quite a bit between the two rounds, this is of little concern at typical self defense practice ranges of 30-50 feet.

More to the point, for our discussion, the .357 offers a substantial boost in velocity and energy when compared to the .38 Special.  Even the ‘+P’ version of the .38 made for modern pistols does not come close to equaling the power available from the .357 loaded to full pressure.
The higher pressures of the .357 Magnum requires a somewhat beefier build to the pistol, but weight and size comparisons between snubbies of both calibers show them nearly the same.
The choice facing us is not really one of weight or dimension, but power.  Control ability and muzzle blast come into play, as does recoil.  The .357 does not get it’s nearly doubled energy over the .38 Special without a cost.  While a .38 snubby might be relatively comfortable to shoot for most people, the same pistol in .357 has a ….. ‘snappy’…. recoil that nobody sneers at for long.   Perhaps that’s why so many revolver shooters enjoy the ability to practice with .38 ammunition, but carry defensively with .357 Magnum rounds in the chamber.

This is a point Carteach agrees with.  Given the choice between the same pistol in .38 Special and .357 Magnum, it only makes sense to buy the magnum version.  One can then always shoot the lighter .38 loads, and even carry them if desired.   I consider it a cost-free option, as the magnum pistols are generally no larger or heavier than the .38 version these days.
As for ‘stopping power’, that has always been a nebulous term.   The fact is…. pistols don’t generally knock people over.  They punch holes in them, and if nerve centers or major bones are hit, the fight is generally over.  Otherwise, pistol level rounds just punch holes and mess things up.  Yes, they will eventually knock down just about everyone…. but that notion of a bad guy hit with a bullet from a pocket pistol, and immediately doing a double backflip over the railing and falling into the volcano…. only in the movies.

That same reality holds with both .38 Special and .357 Magnum.   The only real difference between the two is velocity and energy.  Both, kept to proper bullets for their velocity, have excellent track records in self defense.  The .38 Special holds it’s defensive position well when stocked with the old FBI load….. a 158 grain hollow point lead semi-wadcutter bullet.  This bullet punches holes, and messes things up, and that’s all that can be expected.
The .357 Magnum, with it’s higher velocity and energy, makes bigger holes and messes up more stuff.   As simple as it sounds, this difference is significant.  Very significant.  As a result, the .357 Magnum has a substantially better first shot drop record in defensive shootings.
If one can deal with the recoil, muzzle blast, and control issues of the .357, there is no reason not to choose it over the .38 Special.   As said….. one can always just stoke the pistol with .38’s instead of .357’s.  That said….. The Fat Old Man would not feel undergunned with the ancient .38 Special, given an understanding of it’s limitations.  There’s been a representative sample in his collection for many, many years indeed.  It fills a niche nicely, serves it’s purpose without fanfare, and has the most important feature possible in any defensive weapon….. it works.