Can I vote for the .327 Federal after looking at the muzzle energy charts on that site?
Ballistics out of a 3" barrel (using the strongest loads listed):
.38 Special Speer 135gr- 892fps 280ft-lbs
9mm Cor Bon 115gr +P- 1245fps 390ft-lbs
.45ACP Cor Bon 185gr +P- 999fps 415ft-lbs
.357 Magnum Cor Bon 125gr- 1271fps 450ft-lbs
.327 Federal Speer 115gr- 1316fps 440ft-lbs
That little .327 brings the heat! Then factor that you can throw 6 of those in a J-frame that normally only holds 5 .38 rounds! Out of a Ruger GP100 with the 4" barrel it dials up to 600ft-lbs and you hold 7 shots. That thing is straight nasty, why would you even bother with a .38 Special when something like that exists?