op says for use in ruger gp100 4.2 inch stainless steel revolver
Heavier bullets give you better penetration when hitting things that are more solid. They also fare better in shorter barrels in that they relatively lose less velocity because of the shorter barrel than the high velocity rounds.
The 38/357 magnum works great at 158 grains. I use Hornady XTPs in 158 grain. People hunt deer with it. It'll work on self defense too.
Always .357 magnum. I have a Chiappa Rhino, so no problems with recoil.