The Is2 definitely seems better even though they are of equal cost.
The rate of fire, mobility and armor and penetration give that unit an advantage. Deflection and main gun damage are good, but vs infantry the ROF on IS2 is better as is it's armor and mobility vs tanks.
The Siege mode does not seem very useful most of the time as it presents the teardown liability.
It's not a bad tank, but a slight price decrease, or an improvement on reload with veterancy might help make it more attractive.
