IS2 vet is similar to the Kv-2 but it seems to be better overall. I don't really feel the tanks perform equally at the moment especially considering the fuel cost is equal. You see Is2 all the time and the Kv2 is not nearly as popular.
KV2 Vet 2
+50% weapon rotation speed, +25% direct fire range, +14.3% indirect fire
IS2 Vet 2
+50% weapon rotation speed, +25% range, +20% accuracy
Kv2 Vet 3
+20% weapon rotation speed, +20% rotation speed, +20% speed, +20% ac/de-celeration, +180 hp
Is2
-30% reload, +20% rotation speed, +20% speed, +20% ac/de-celeration
The situation is exactly the opposite - I see the KV-2 and generally do not see the IS-2. It's not about vet, it's about the main gun - the IS-2 main gun does not cause damage - there is no damage - there is no vet, no matter how good it is.