It's all good, but the IS-2 will continue to miss the tanks / infantry, don't penetrate, don't deal damage (yesterday, Brumbar inflicted more damage on the IS-2 than I did in response)
IS2 has the KTs armor, the KTs penetration and the KTs accuracy.
It has less damage, and worse scatter. Also cheaper of course and you don't need to side-tech for it. I like it more than a Tiger, since its bounces more.