The pak40 has a harder time penetrating a Is2 than zis penetrating a tiger.
The IS2 is still faster, means you can gtfo quicker when a situation becomes hairy.
I usually manage to keep my Is2 alive longer than my tiger, hence the reason why i completely stoped using tigers since they are just vet food for tank destroyers. Especially after the Jackson pen buff.
Don't try to make believe us you play soviet more than 1 time/2 months, or hide your playercard.
This just reinforces my theory the only people pissed about the Sturmtiger are people who are sad blobbing no longer is piss easy against OKW due to lack of counters.