A 4-4-2-8 Heavy Tank won’t make a 3-3-2-6 Tank obsolite, or at least statistically. Here’s why:
We start with the lowest common denominator in IPCs, which is 64 IPCs (6 IPCs x 8 IPCs).
With 64 IPCs, you can either buy 8 Medium Tanks or 6 Heavy Tanks. Interestingly, the attack points for both groups is the same: 24 (Med=8x3=24, Hvy=6x4=24).
However, the Medium Tanks have a clear advantage due to their numerical superiority.
By dividing the number of attack points on each side by 6, we can determin the most likely number of casualties to be inflicted in each round of combat.
I the first round, both sides will inflict 4 hits (24/6=4)
The Medium Tanks are reduced to 4, and are down to 12 attack points.
Heavy Tanks are down to 2, with only 8 attack points.
It’s all over by the second round, where the Heavys inflict one more casualty before they are wiped out.
Victory goes to the Meduim tanks, yet they took heavy losses, 5 out of 8.
Therefor, in the long run, Medium Tanks are the better buy. The more IPCs you spend on Tanks (64 IPCs is a lot, mind you), and the more battles you fight, the more the war begins to tip statisticaly in favor of the player who buys Medium Tanks.
So, considdering this, why would anyone want to buy a Heavy Tank? It all comes down to those extra 1 or 2 IPCs you have left. Do you want to spend them now or later? Many would say “now”, and buy a HT instead of a MT.