Gavi and Pedri have no real comparison or parallels. Pedri demonstrated world-class creativity and technical ability from the off.
Gavi's game awareness isn't even close and he is much worse on the ball. The problem is, he isn't athletically better either, or defensively.
At this point its hard to see Gavi's benefit for the team unless he starts to do better with the ball at his feet. He is not a physically dominant or defensively dominant midfielder and not particularly good at defending either, so if he doesn't add things in the offensive phase, he is not very useful.
There are much better ball winning midfielders to put in his place if that is what is needed. Frankly, I think we'd have been far better off without him in the side and its hard not to notice that the side seems to be much better with him out of it.
He is much more comparable to Pablo Torre and Fermin than any of the other midfielders, though, I don't think he is better than either of them at this point. Fermin is improving quickly and has shown goalscoring instincts as well as technical and athletic improvement. Pablo Torre is technical and can put a good ball in.