IS-6 or 112?

I am thinking of getting either the IS-6B from the bond shop or picking up the 112 from my next referral contract and I noticed the tanks happen to be nearly identical. They both are pref mm tier 8 heavies with nearly identical guns and good armor. The 112 seems to have a better upper plate, IS-6 has a better lower plate. I don't need crew trainers for Russian heavies so that is a pro for the 112, but the tanks seem to be so similar that I see no reason to pick them both up since they are so similar. Does anyone have both? Are they only similar on paper? Which one is better for credits?

Edit: I realize there are much better premiums out there, and I have way better premiums. It's just that the IS-6B is the last tank for me to get from the bond shop before rotation and the 112 is 1 of 2 tanks I want from a referral contract. They are just so similar I only want one of them. I either save the bonds for the shop rotation or get the 2nd tank from the referral contract.