I don't think it's even arguable that Steph peaked higher than Kobe, there's too many supporting points to make for Steph and not nearly as many in favor of Kobe...
I'd still favor Kobe right now historically, because of the two points I mentioned earlier, I think the Comeback Kobe run is one of the strongest individual cases any GOAT can make considering all the noise around him (aftermath of rape case, beefing with Phil, beefing with front office, can't win without Shaq narrative) and the relative talent on his team in comparison to other GOATs when they won...
And the fact he was an elite player for somewhere between 12-15 years. Steph is "only" at 9 years as an elite player, and I'm using "only" facetiously because that's healthy longevity of nearly a decade. Steph is knocking on that Kobe door easily though, if he extends his prime another year or two and there's more information to add into the evaluation of his career, I'll probably change my opinion...