It's interesting to see the difference in thinking between the US and the Germans in their development of armoured fighting vehicles. It seems that the Germans focused on heavier and heavier tanks as the war progressed. You can see a clear linear evolution in the Panzer series from the I,II,III,IV up to the Panther, Tiger and King Tiger.
The Americans however did not seem to follow the same thought process and from my limited understanding seemed to favour putting bigger guns on motor gun carriages whilst keeping the Sherman as the main tank despite it's vulnerabilities to the heavy German Tanks. From what I've read, the Pershing didn't really seem to have that much impact on the war when it finally arrived towards the end of 1944 in the European theatre.
I'd be curious to know a bit more about the US reasoning for this.