While Soviet tanks have thinner armor than other nations, they make up for it by having highly sloped armor which increases effective thickness and a higher chance to ricochet shells. Their guns also pack the most punch in the game and along with their good speed, maneuverability, and armor characteristics, make them kings of close combat. Their downside is that they have poor accuracy and aim time, and in some cases a low rate of fire.
Soviet light tanks are typically the fastest in the game and, like most Soviet tanks, have a small frontal profile and sloped armor.
Soviet medium tanks are also fast and maneuverable, but in order to make the tanks compact, engineers placed ammo storage in very vulnerable places, increasing the chance of ammo rack detonation.
Soviet heavy tanks have the best values for everything except accuracy and aim time; their frontal armor thickness and slope makes them quite difficult to penetrate from the front.
Soviet tank destroyers are not as well armored or accurate as their American or German counterparts, but they offer increased speed, agility, and brute firepower.
Soviet self propelled guns are generally quite accurate but don't do much damage. However, they also generally fire their shells in a very high arc, making their flight time long, but able to hit tanks hiding behind rocks and small buildings. They also tend to have higher firing rates than their foreign counterparts.