One difference of major importance between Black & Smokeless is that black will retain a near constant burning rate regardless of other conditions. You could for instance load a 10 gauge down to a oz shot load & get everything out the barrel with no problems. Smokeless on the other hand burns faster as pressures increase & of course slower under low or no pressure. Note that in the chart Drew posted that only "Oval" (a slow progressive powder) had a max pressure lower than did Black.
PB is a great powder, "BUT" personally I would be extremely leery of any load with it which gave a lower max chamber pressure than black with an equal shot load pushed to the same velocities. I have seen published data which showed Black in a 12 ga pushing 1 oz shot loads to mild velocities as being down in the 4k range for max pressures. As my loading has always been more for hunting loads to be used in cooler weather than on a range in sweltering heat I prefer loads up around the 7K range when using fast to medium powders & don't like to drop below 8K with slow powders, they just burn better at these pressures. "IF" a shotgun won't take those kind of pressures it stays on the wall at my house. One of my long time favorite powders ever since its introduction has been Green Dot for use in mild loads for my Damascus guns as it easily meets my pressure requirements & has been readily available at more economical prices than may others.
