For the record the exact buff is 20% reduction in damage, which equates to 25% additional effective health. 20% damage reduce does not equal 20% more effective hp. This basically means that all 640 hp tanks around it get 800 hp, the same as a t34 85.
Also Im gonna have to go with the others and say that the command tank can't take on any medium tank since it does basically half the damage of every other tank with even shittier pen even with the health advantage it has.
To put this in perspective; the tank has a 30% chance to frontally pen a T34/76 and a 28% chance to frontally pen a short-gun Sherman (at max range that is, although close range isn't much better since it has almost flat pen at 55/50/45)
It would also take 8 shots from the CPIV to kill either of those tanks, but if we factor in the low pen chance and standard RNG it would take 26 shots