FACTS:
Some revolver which are 100% capable of shooting .38 Special +P were manufactured before SAAMI created that designation so a +P has no way of being on the barrel. It's like a counterfeit Roman coin marked 300 BC, who would they know that year was Before Christ was born?
Next, "most" commercial .38 ammo marked +P today is no hotter or even lighter than the normal .38 Special ammo that was around in the 70's before the lawyers got involved. So much of what we shoot today is dumbed-down and made acceptable for the super light handgun now being carried. Same holds true with .357 Magnum ammo. Just look at Speer short barrel .357 Magnum ammo, it shoots a 135gr bullet @990 fps. Back in the 70's most 158gr .38 Special ammo was doing that velocity.
What I would do, practice with standard ammo and carry +P ammo but not because the +P ammo is so much better but because the bullets used in that ammo are so much better. Good SD ammo in standard pressure is very hard to find, if at all. Federal Nylcad and Winchester Silvertips are the only ones I can think of right now and try to find those!