Check out this project made by “Cheezix”:

We can now calculate the experience and credit costs of each tank, there is also a compare option so you can see which tanks are easier/cheaper more easily.

Cheezix says: “It seems the German tanks are the fastest
tanks to grind and some Russians (if going a detour) taking the most time
and effort. I made this little summary in a table so it's easy to check.
I hope it will proof to you even though the game is made by Russians, they
do not always benefit the Soviet lines in every way.”

(NPTA: Not paid to advertise)