13/7 is usually solid - it forces your enemy to care about piercing but has decent HP:IC ratios. Next up, you have to figure out what ratio to use. Amtracs are pretty essential as the Axis for killing the USSR, and for the Allies they're needed for naval invasions (see template 4.2) But primarily defensive nations like the USSR can stick with standard mechanized (and frankly anyone can, you just have to force attack rivers). However there are some countries, like France and South Africa, where it's unavoidable (at least early game). Generally, for heavies, you don't want to use motorized if you can avoid it, since it negates a lot of their biggest advantages. First off is the question of motorized, mechanized, or amtracs. Variants: Here's the real meat of this post. But that doesn't mean medium tank Soviets isn't viable. Personally, I do heavies if I only have 1 or 2 tank research bonuses, and would only do mediums if I had 3. Most importantly, heavy tanks are near-impossible to counter with AT infantry, unlike medium tanks. But in general, heavy tanks will do better at defending chokepoints and winning tank-on-tank battles.

medium tanks is still strong and it's definitely a matter of personal preference.

If there's a 1-size-fits-all 'outline' for (MP) tanks, this is it. Template 4.1: The 40 width '13/7' heavy tank division.

Hoi4 armored division template