Well the T55 is one of the most numerous tanks on the battlefield in modern times and serves with many different countries hence why that was chosen, the Elefant only ever numbered 80 tank destroyers was issued in July 1943 35 were lost at Kursk they then sent 1st Company to Italy to fend of the British invasion and the other 2 companies went back to Russia were they served until early 45 when they were replaced by Jagdtiger, the last 3 were sent to Berlin, though not the most reliable of tanks once they were able to defend themselves the remaining 40 odd tanks caused a lot of damage, for some reason this tank has mystical value and every man and his dog has tried to get an Imai version for years.

To answer your question, then why build not one but two types of Sherman they weren’t called “Tommy Cooker” and “Ronson” for nothing