The Police Positive and Police Positive Special revolvers were of equal strength within the particular time they were produced. The only difference was cylinder and frame length. Those made from the 1920's forward can use the British .38-200 load, or the old Winchester 200 grain Super Police cartridge. This is why Colt continued to make, and export, limited numbers of Police Positive Special/.38 S&W revolvers after World War Two. At the time there was almost no demand for this gun/cartridge combination in the United States however.
Smith & Wesson did the same with their Military & Police/pre-model 10. Few people realize it, but the .38 S&W is the second most common chambering in the K-frame M&P revolver, next to the .38 Special, although it was not introduced until 1940, and never cataloged for sale in this country.