+P ammo is the solution to a problem that doesn't exist, wasted money no matter the gun. Lighter loads are NEVER more effective than heavy loads, especially in 357mag. Your gun was designed for 158gr lead bullets. Stick with them, you won't be disappointed.
I've never seen anyone argue that standard pressure rounds are every bit as good for defense as +P rounds in .38 special. There may be adequate loads in standard pressure cartridges but just as good as +P? I am curious as to your reasoning.