Greb. Ward would not only be given a boxing clinic on workrate and movement, but also a clinic on fouling, should the rough stuff break out.
I rate Ward very highly for skill and all round ring savvy. He showed he could handle the bigger man in his fights with Kovalev which of course Greb did routinely. He was also a master of the dark arts which would hold him in good stead against Greb. In some ways these two are similar in that they'll seemingly do anything to win, both mentally very strong. Opponents always find Ward extremely awkward to fight, he takes them out of their rhythm, but in the awkward stakes I suspect he'll have met his master with the non stop perpetual motion of Greb with the angles and the intensity. It's difficult when there's no film of Greb, but you would have to take him simply on his resume ranging from beating ATG fighters from middleweight to heavyweight. It would go to the judges though, and I'd take Greb to win a hard fought UD.
I`ve never seen Greb fight but Tunney beat him and Ward did the same stuff as Tunney so that might prove something, also Ward handled Kovalev well, no one knows if an aggressive come forward fighter like Greb could beat a long puncher like Kov, also Greb doesn`t look as tall as Ward so Andre would have the savvy to keep him at the safest range maybe.
I think you objectively have to favor Greb, but just to go a little bit against the grain here, from my understanding of Greb - the things he did well seemed to have been best neutralized by opponents with a tremendous understanding of distance. Guys who consistently knew where to be, when to be there, and how to get there. While many here will be apt to dismiss Ward out of hand, I think his understanding of distance makes him an extremely tough draw, even for a true great like Greb when at his best.
Tunney had 12 pounds on Greb .. Ward wouldn't have that weight on him .. And Greb beat Tunney in I and in II as well( according to vast majority)... .. BCS8 has it right here ..