Myth: Soviet optics were abysmal, and their guns inaccurate, to the point where they could not engage enemy targets at more than a few hundred meters.
Fact: Soviet guns do not lack mechanical accuracy, and are occasionally more accurate than their German counterparts. As for optics, Americans praised them at Aberdeen trials: "Consensus: the gun sights are the best in the world. Incomparable to any currently known worldwide or currently developed in America.".

Myth: The T-34 was a very unreliable tank, as proven by trials at Aberdeen.
Fact: While trials at Aberdeen uncovered some flaws in early T-34 tanks, the tank sent to them was an obsolete model that went through major refurbishment. Furthermore, American testing was flawed (for example, they failed to oil up the air filter). Read more details here and here.

Myth: Soviet Cold War era armour was abysmal, and the Americans had nothing to fear from it.
Fact: The CIA disagrees.

Myth: Western Armor Proved Superior to it's eastern counterparts during Operations Desert Storm and Iraqi Freedom
Fact: The most modern tank the Iraqis Fielded was the T-72, the export version that the Iraqis had lacked the modern optical and target systems most Russian and former Soviet Block tanks field. Furthermore these tanks were poorly deployed in hull down positions in the sand, the Iraqis did not make use of proper tactics.
The 125mm rounds used on these T-72s was manufactured before 1973, this ammunition had long been out of service in the East Block.
During the Iran Iraq War, the T-72 saw action against its British Counterpart the Chieftain, there are numerous accounts of T-72s knocking out Chieftains without a single loss, furthermore Iranian TOW missiles proved to be ineffective against the T-72. Account of an Iranian tank crewman here

Account of a Syrian T-72 tank crew member

More on the T-72 here

Myth: Order #227 of the People's Commissariat of Defense, nicknamed "Not One Step Back", allowed for executions of Soviet soldier and officers without trial by commissars for retreating.
Fact: Many people have heard of the order, but never actually read it. The text of the order states that officers that retreat without authorization are to be relieved of duty and face court-martial. Court-martial for disobeying orders is common procedure in any army. "Panickers and cowards should be executed", however, did allow for overzealous interpretation. The order is also frequently confused with Order #270, which allowed for execution of any commander or political worker that removes their rank insignia and flees to the rear or surrenders to the enemy.

Abrams vs the T-90