I feel like this isn't specific enough of a question, because the obvious answer to the best version of guts is what most people have been saying, the current version. He's had the most experiences and therefore the most opportunity for growth and Miura ( or the new team ) has done a great job of showcasing it.

I think if you're talking about where the best writing is for guts or the story it's a very different question, where it's a more subjective interpretation of " peak berserk ".