Povetkin. You can tell quite easily the difference in skill by watching the two of them fight. Kownackie looks easy for Povetkin to land on, and depending on his chin stop.
Kownacki appears to be tough and can punch but as already pointed out Povetkin is a step above in terms of ability, so I think he wins by decision.
This content is protected Kownacki is only a part-time boxer. Afaik he is a student in NY, majoring in business. You can see he likes to fight, he is tough but limited so far. He could have a chance to beat Wilder and Pulev for example, but I don't think he can beat a skillfull boxer like Povetkin or a very big guy like AJ.