I'm going with Eubank, although I think it's a close one, just my dislike for Toney as a person tipping the balance
I can see your logic but I can't recall any wars at heavyweight for him to be honest. Both him, against Jirov, and Eubank, against Thompson had a war at Cruiserweight but I'm going to go with Eubank because of the Benn fight which, in my opinion and at the risk I've forgotten any Toney fights, was a tougher war than anything Toney had and just, though only, gives the nod to him.
If using 'chin' as a term for overall punch resistance, then Toney edges it, as Eubank occasionally had issues taking body shots.
Really? Eubank was stopped by Thompson, war though it was. Toney was battered by prime RJJ when he was severely weight drained.
He was, but he was also getting battered at that stage. Great chin, for sure. But Toney was still fighting it through heavies when... well, look at him.