I shot regular load .357 rounds and .38 plus p in my .357 and I have to disagree with you. Those .38 plus p are pretty good. But as I said the .357 rounds I was shooting were regular target type loads. I only did this as a comparison between the two..
There used to be a .38/44 Outdoorsman load which was pretty close to .357 magnum. I have not seen any in a while but probably still available.
From http://www.gunnuts.net/2012/06/13/38-special-p-vs-357-magnum/
Comparing loads side by side shows that .357 Magnum still has tremendous advantage in muzzle velocity over a .38 Special +P if loaded by the same factory. For example, the Hornady Critical Defense .38 Special +P is pushing a 110 grain bullet at a stated velocity of 1090 FPS, which would produce 290 foot pounds of energy. ... the Hornady .357 Magnum Critical Defense load is pushing a heavier bullet at 125 grains considerably faster – 1500 FPS according to Hornady. That gives us energy of 624 ft-lbs, which is…more.