In game-useful terms, comparing the T-34/76 and Panzer 4 F2/early-G (The two tanks modeled in-game currently):
The T-34 had (significantly) superior armor to the Panzer on all facings (It is more protected on the sides than the Panzer is in the front). It had a slightly higher on-road speed, a significantly higher off-road speed, and a significantly higher power-to-weight ratio (Note that the game uses on-road speed, despite the off-road terrain, rather axing the T-34's advantage here).
The Panzer 4 had a more powerful gun, with better optics.
In terms not really useful for the game:
The T-34 is cheaper, more reliable, and easier to maintain.
The Panzer 4 has a radio in every tank, improving coordination between vehicles. It has a separate gunner and commander, improving crew efficiency and situational awareness. It also has a commander's hatch that isn't so stupidly designed as the T-34's.
In every useful comparison of stats that should matter for this game, the T-34/76 and Panzer 4 F2 are fairly even in firepower-to-armor, with the T-34 having slightly better protection against the Panzer's gun than the other way around, and with the T-34 being much more maneuverable. Taken just from that, the T-34 is easily the superior tank. The elements that don't really matter in this game, such as the separate commander and more frequent use of radios, often led to the Germans having the advantage in tactics. This often gave the Germans the advantage despite the otherwise superior Russian tanks, but that's something that would be hard to model in-game.
And you really can't discount cost and ease of production. By a quick skim, it looks like Russia produced more T-34/76s from 1940-1944 then Germany produced
tanks, of any kind, throughout the entire war. The ~6,000 Panthers that Germany managed to produce in the last 3 years of the war? Russia made as many T-34/85s in 5 months.
As for this:
Panzer IV was created to destroy T 34 76. T 34 85 was created to destroy Panzer IV. Panther was created to destroy T 34 85.
You should really look up the actual history of the tanks more. The Panzer 4 was created as an infantry-support tank. The F version that first encountered the T-34/76, in 1941, was found to be severely lacking. They cobbled together a quick fix in the up-gunned F2 (Or early G) version, but this was a band-aid rather than a real fix. It let the Panzer 4 actually fight against the T-34/76 without being
completely outclassed, but it was still leaning in the Russian's favor. The real "counter" was the introduction of the Panther tank at the very beginning of 1943, which not only carried over the superior firepower, but finally offered a German tank with superior armor protection (And, tellingly, had a design very much like that of the T-34).
The Panther was most definitely
not created to destroy the T-34/85, as that tank wouldn't even exist for more than a year, in early 1944.