SHERMAN, according to Wiki, the T44/85 did not see operational use in WWII … even though it was in production as you said. So, it falls in the gray area along with tanks like the Conqueror, Centurion, JS-3, etc …
The Comet did see use in WWII … but obviously by the time it got into the fight, the die was cast. If they were Jumbo Shermans instead, the outcome (except for a few allied crews, perhaps) would have been exactly the same.
Monty B, good point. If the object of this thread is to ask, “Which is the best single vehicle, period” then your challenge is valid. If the definition of ‘best’ vehicle includes its ability to fulfill its intended role, then I think my point remains (at least partially) valid.
I assume the role of the King Tiger was to protect the German homeland against the armed forces of the Allies. And in this role, it was not particularly effective as it was unreliable, a big fat target for Allied aircraft and too few in number. The Panzer IV Ausf J was a good match for a Jumbo Sherman, late model Cromwell or a T-34/76 so having a few thousand more of those vehicles would have been a useful resource … although experienced tank crews were also in short supply … this is not a simple issue.
Not sure if it would have been wise for Germany to stow all their eggs in the Panther tank. On paper, I think it was the best design of the war but it had serious driveline problems and was expensive to build.
Since the Germans were on the defensive most of the time, building more (simpler) Jagdpanzer vehicles for ambushing Allied armor probably would have given them the best bang for the buck.