I think you both, LG and GrG have a slight misunderstanding in penertration of rounds. GrG is right in thinking the more rounds, at a higher velocity would cause more damage and, yes LG is right in thinking the heavier round causes more damage by looking at its size. But you have to look at how many, how fast, at what speed and where all together.
A Pz.IV Ausf G (Medium Tank) could take a direct hit from a 20mm anywhere on the tank from any range (except from a certain German 20mm shell but why would they shoot their own tank?). Even with this several hits, at high speed, in the same general area would destroy the tank. Most 37mm could pierce its armour (Rear and Top) so the IL-2 could do it effectively, but would still take some doing. It's not one round, the tank is dead.
Now, talking of Pz.V, Pz.VI and Tg II it's a completely different matter. Plus you're all missing out the German SPGs one of which (a great difficulty for the Soviets and Allies alike) the Pz. Jag Tiger (P) or Ferdinand for normal people. One 37mm would struggle taking out the Ferdinand from the top, let alone anywhere else. It was impossible, and I repeat impossible, to destroy these things from the front with 37mm or 20mm shells. Rockets would be needed for taking out Tg. IIs and Tiger (P)s. The Ferdinand had 200mm armour for Gods sake...the T-34s and Kv-1s of the SU didn't stand a chance, let alone the Sherman. Anyway, a little off course here.
The Tiffy had about the same penertration with guns as the Il-2 because the Il-2 had heavier, but less guns, with slower speed of round, and slower rate of fire. Example of gun being smaller but a heavier hitter; The 75mm KwK 42 L/70 (Gun on the Panther) had a penertration of 194mm at 100m. The 88mm KwK 36 L/56 (Gun on Tiger) had penertration of 120mm at 100m.
On the production, the Soviets were unwilling to break the production runs, that's why they loved the T-34, because things like new turrets, improvements or armour upgrades could be added into the production with little or no disruption.