Back in the dark ages my dad flew Lockheed Electra (188) line #3. Before it was delivered to the customer (L.A. Dodgers) it was used as a test bed for upgraded engines and props. The engineers always said they preferred the Ham Standard (Round Tips) props as they were slightly more efficient than the Aeroproducts (square tips). The Aeroproducts were cheaper and that was what the airlines ordered. (except KLM) The increased efficiency was not enough to offset the initial cost. My guess is that the bean counters usually win.