In *independent* testing P-dex is worst, T-7 second, BP third in corrosivness. T-7 is about 1/2 way between p-dex and T-7. I think T-7 is about 20-30% perchlorate. Its a revised P-dex which has far more perchlorate. T-7 is covered by the P-dex patent if I am properly informed.
I am also told that the perchlorate fouling will rust under an oil film.
If these perchlorate powders are used in old guns with existing pits its very difficult to get the rusting stopped. Not matter how much water you use.

The P-dex/ t-7 residue is highly corrosive and even a 1/2 grain or less in a primer (Potassium Chlorate in primers) will eat bores as a frightening rate.
BP is basically non-corrosive at less than 30% Relative Humidity.

I can only speak to what I have seen, experienced and had reported to me over the years. I either shoot BP or smokeless. I avoid the synthetics.
I am alarmed that Hodgdon now controls not only Pyrodex etc but also Goex. The profit margin for Goex's sporting BP line is not all that high I am told....

Dan