USSR
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, and equipped with accurate guns unlike the other lines in Russian tree (and gets even better in high tier). All are jacks of all trades and very versatile. Unfortunately, most suffer from poor gun depression, limiting their ability to go hull down and makes use of their strong frontal turret.
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. There are two lines: the KV line which offers thicker armour and standoff potential at the cost of mobility and the IS line which has armour more reliant on angles, but better agility and alpha damage for brawling.
Soviet tank destroyers have bad armor but they have best accuracy in game. They offer increased speed, agility, and brute firepower. There are two lines: the Object 268 line which favours alpha damage and the Object 263 line which favours mobility and Damage per Minute.
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.
Light Tanks
Medium Tanks
T-29
A-32
T-28E with F-30
T-34 avec L-11
T-28
Matilda IV
T-34 shielded
M4-85
T-34
A-43
T-34-85M
T-34-85 Rudy
Loza's M4-A2 Sherman
T-34-85
A-44
KV-13
T-43
T-44-122
Object 416
T-54 first prototype
T-44-100 Igrovoy
T-44-100 (R)
STG
STG Guard
Object 274a
T-44
Object 430 Version II
Object 430
T-54
Object 140
Object 907
T-22 medium
K-91
Object 430U
T-62A
Heavy Tanks
Churchill III
KV-220-2
KV-220-2 Beta Test
KV-1
KV-1 shielded
KV-1S
KV-2
KV-2 (R)
KV-85
Object 244
T-150
IS
KV-3
KV-122
IS-2M
IS-2 shielded
IS-2
IS-3
IS-6
IS-6 B
KV-5
KV-4
IS-5 (Object 730)
IS-3A
IS-3A Peregrine
Kirovets-1
KV-4 Kreslavskiy
Object 252U Defender
Object 252U
IS-M
Object 703 Version II
IS-2-II
T-10
Object 777 Version II
Object 257
Object 705
IS-3-II
ST-I
IS-4
IS-7
Object 260
Object 705A
Object 277
Object 279 early
ST-II
Object 780