The .38 special is only effective as the rounds used.
The .38 special isn't effective as the 9 mm or the .40 S&W which have replaced it on most major police forces in the country. However, that being said it will work with the right rounds. Since it is actually a .36 caliber balistically, not a .38 caliber. How that confusion ever happened I never understood. Anyway, I would think that Heavy level +P rounds would be the most affective rounds for the 38 special.
Here's how they rate in real world street shooting. (Not that one shot stop stats really mean that much)
.38 Special Caliber: 2-inch Barrel
One Shot Stopping Success: 49-67% (Actual)
Self Defense Rating: Good
Recommended Cartridges:
Winchester +P LHP 158 grains 67%
Federal +P LHP 158 grains 66%
Federal +P JHP 125 grains 65%
Remington +P LHP 158 grains 65%
CCI +P JHP 125 grains 64%
The effectiveness of the .38 special really goes up in the 4 inch barrel.
.38 Special Caliber: 4-inch Barrel
One Shot Stopping Success: 51-83 % (Actual)
Self Defense Rating: Very Good
Recommended Cartridges:
Cor-Bon +P+ JHP 115 grains 83%
Winchester +P LHP 158 grains 78%
Federal +P LHP 158 grains 77%
Federal +P JHP 125 grains 73%
Remington +P SJHP 125 grains 73%
Winchester +P+ JHP 110 grains 71%
CCI +P JHP 125 grains 70%
Remington +P LHP 158 grains 69%
The .38 special may not be the best self defense round available today,but it will do the job with the right rounds.