It could be a fair swap depending on subjective scouting opinions of the players themselves... I don't think either one of them has a large enough body of work yet for a very conclusive consensus to exist. If our Preds scouts thought that Kravstov was definitely going to be a 20-goal NHL player with a bit more of power game, I could see them taking this deal, since the organization does seem a little reluctant to really embrace Tolvanen. I think they're undervaluing Tolvanen, he is playing really well at both ends from what I can see, and should have a bigger offensive role too. But if they were really sold on Kravstov's potential, they might like him more.
However... the main catch is that the Preds need a player RIGHT NOW. Tolvanen is a good player right now, and he's pretty affordable, and I think the Preds very much need him in the immediate term as they attempt to make the playoffs. If it's more likely that Kravstov still requires time before he's ready to contribute as an NHL regular, then I don't see how the Preds could make this deal, even if they really liked Kravstov. It would have to be more of an offseason deal than one they could think about right now.