I dont think Hischier will be as dynamic of a scorer when compared to Kuznetsov, but he does make up for the offense in the other categories. I see Hischier as a similar type player as RNH. Solid two-way guy who will score but not as we had hoped for from a 1st overall pick. People (especially in fantasy circles) will perceive this as a slight against Hischier but in real life, he will be an excellent NHL player.
A lot depends on who they surround him with. They had the first overall pick last year and took another center in Jack Hughes, who does nothing to help Hischier going forward. When Hall was there, Hischier really took another step forward offensively. If NJ can build around Hischier then I think he's going to be awesome. If they build around Hughes, that means Hischier will be relied on more as a two way guy compared to a true 1C.
All that being said, I guess it depends on what you need more. If you are lacking offense, and can afford to sacrifice some fo the other key categories (FOW, takeaways, blks) then I'd probably go with Kuznetsov. If you like the idea of a more balanced player, then I'd go with Hischier. He will still offer solid offense but not to the extent that Kuznetsov will.