Stalin 3 is an intersting monstrosity, it's turret side armor was thicker than Tiger II turrent frontal armor. But Stalin 3 itself was never figured out nad it took years nad years of modifications and rework to new models JS3M and T10 for it to work right. The design was too ambiotions and soviet consturtion methods were not up to the task - the things literally fell aprat at the weld seams on road marches.
Centurion saw no real use in WW2, but it certainly stiod the tesat of time after the war becoming one of the best and most adaptable tankl designs ever.
I think brits came out with a couple of great new designs late in the war with centurion and Comet. Though the Comet was silly in part because of its outadted vertical glacis.
Panzer IV is an awful design, a real production monstrosity and it it truly took so much time to bold this bucket of aftertought together that it was only a bit cheaper than the 45 ton panther. Go look at a Tamiya or DML model of a Pz4 to see just how bad the design was for production. But on the othewr hand it mounted one hell of a gun for a 25ton tank and pretty decent frontal armor in the later models almost as much as tiger.
