Speaking with sport.ua, Yarmolenko was asked to rate the pair.
He replied: "It's hard to make a choice.
"I asked a lot in Dortmund about Klopp, how he works. Everyone is excited about him.
"I've asked (Oleks) Zinchenko and the other players who worked with Guardiola, too, all are excited. Never heard anything bad. For me, this is a difficult choice. These are the two best coaches in the world."