All that I know is my own experience.
Older Stainless, less reliable, but after fixing a few times, VERY accurate.
Newer Stainless, tend to break magazine release as it seems to be made from an inferior casting metal. I wonder if Smith and Wesson had the magazine releases made from some sort of junk metal as there was not this problem with the stainless TPH bought from Interarms.
Blue, Interarms American, far fewer of them were made. Generally a little more reliable than the stainless, but still NOT perfect until worked on a time or four.
German alloy, very rare in this country, very much sought after by international undercover agents.
Other German TPHs, very rare in this country as there were few sold here, due to the very high cost, before 1964 gun laws and then none were sold here, except to various federal secret police types after '64 gun laws went into effect. Thus, VERY rare here. I think there is also a very rare German stainless... not certain however.
My favorite are the American TPHs as they seem to be more well made as far as quality of metals used. The fit and finish on the German blued steel is flawless, of course. However, the fit and finish on the Interarms is very nearly as good or equal to the German.
All in all, the difference in prices seems to be based on scarity alone. Smith and Wesson DUMPED hundreds (if not thousands) of TPHs on the market at dealer cost of $300 or less, in the first few weeks after they bought the remains of Interarms stock and parts.
