If your need of it is for personal defense I would go with the .38spl+P. Most .357mag revolvers are a little beefier and will add mass and weight to your carry. As far as ammunition goes, the .357magnum is more versitile if you wish to hunt and shoot through barriers, but the .38spl would be more ideal for defense. It is more controllable and has less blast and flash. As far as terminal effects go, against a human target which has an average torso depth of 9" from front to back, you really gain no advantage in using .357magnum.
The .357magnum earned its “manstopper” reputation in the early days of hollow point design which was from about the late 1960s to the late 1980s. During that time period ammunition manufactures tested their hollow point designs in water tanks. Water does not compress. So, when a hollow point bullet impacts a hydraulic substance the water that is constantly being fed into nose of the bullet as it penetrates must escape at the weakest point of resistance. That weakest point is along the sides of the hollow point. So, the hydraulic force opens up the hollow point and causes the mushrooming effect. The problem with the water tank testing is that human tissue is not 100% water. So, the hydraulic forces involved in shooting a person are weaker than that of a water tank. This problem was very evident with lower velocity loads such as heavier bullet weights in 9mm, .38spl, .357mag, and .45acp. The poor engineering behind these early hollow points made for unreliable performance unless you cranked up the velocity of the bullets and used lighter bullet weights(this of course led shallow penetration characteristics with the 9mm and directly to the deaths of two FBI agents in 1986). In this time, the .357magnum was the ideal cartridge because it had the velocity to open up these poorly designed early hollow points and still have deep penetration.
In the 1987 FBI Wound Ballistics Workshop various calibers and ammunition types were tested and this problem was exposed to the ammunition industry. Since then, ammunition manufacturers started testing their hollow point designs in ballistic gel which more accurately mimics the density, elasticity, consistency, and water percentage of human tissue. With a more accurate model to standardize their ammunition by, calibers like the .357magnum and .357sig simply offer no measurable advantage over calibers like the .40S&W and .45acp which enter the body bigger, penetrate to ideal depths, and expand to larger diameters with consistent reliability in actual shootings. Also, the 9mm is capable of damaging more tissue and penetrating commonly encountered barriers better than the .357sig due to its ability to use longer, heavier bullet weights such as the 147gr bullet. The .357magnum can be loaded with much heavier bullets like the 158gr and 180gr, so it offers better capabilities over the 9mm should you wish to hunt or shoot through barriers.
The law enforcement trend in the 1970s was to move towards the .357magnum because it seemed to do better in the field over the 9mm, .38spl, and .45acp. As I mentioned above, it performed MUCH more reliably with early hollow points and actually expanded to a diameter greater than that of any of the other calibers. So, it damaged more “stuff”. There was none of the mythical energy dump, or other assumed effects to the body that were a result of impact energy, pressure wave, or neurological shock. With the technological advances in bullet designs in the last 20years, things have changed. The law enforcement trend of today focuses on the big three calibers which are the 9mm, .40S&W, and the .45acp…….very distant is the .357magnum and its auto clone the .357sig. Not only that, but the trend in ammunition use favors heavier bullet weights which penetrate more deeply and reliably than the light and fast, high kinetic energy bullets. Equipment trend is a direct result of measurable and observable results.
Unfortunately, ammo manufacturers are not producing as big of a variety of defensive loads for revolver cartriges as they do auto cartridges. A very good performing .38spl load which does well both in longer barrels and short snub nose barrels is the Speer Gold Dot .38spl 135gr+P. Here's some fired from a 2" barrel:
.38 Sp Speer 135 gr +P JHP Gold Dot (53921), average velocity=856f/s
Bare Gel: penetration=13.1”, recovered diameter=0.56”, recovered weight=134.5gr
Through 4 layers denim: penetration=13.6”, recovered diameter=0.53”, recovered weight=134.1gr
Through auto windshield: penentration=9.4”, recovered diameter=0.51”, recovered weight=129.6gr
Take into account what the bullet actually does to things, not what its advertized velocity is.
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