Pulev probably. Huge gap in technical ability, and much better durability too. I might be completely wrong but it might resemble Thompson vs Price 2, with Wilder taking a the part of Price.
To be fair to Pulev he's very busy and has fought and beaten fringe contenders already. He's probably just above the level of Stiverne in my opinion.
I think Pulez wins. He has decent basics and size etc which is what you need to defeat the wide wide punching Wilder. As well as balls which he has!