JB played in 9 more games last year, but actual production while on the court, Zion produced more WS/48 .159 to .135. That was Brown's career high and Zion was below his career avwrage. They have the same career VORP at 14.1 but Brown has played 4 more sessons. Zion has a better OBPM by far in their careers and they were the same lat year. Brown hasn't had a positive DBPM since 2022 and the only ither positive was 2018.
Zion definitely has more durability concerns, but he is also 4 years younger. But actual on court production Brown is not way more productive even comparing his career year last year to a down year from Zion.
It is true that Zion played 62 games in 2025-26, albeit <30 min per, but that is only the 3rd time in his 7 seasons that he has played more than 60 games. The other 4 seasons range from 0 to 30 games. Assuming that this one season means that his durability risks are behind him is a huge leap of faith. They might be, but more likely, load management will be a issue for him the rest of his career, like Porzingis.
As to demonstrated past performance/production, sorry, Brown is currently and has been better. Sometimes reading stats is like reading horoscopes. You can see whatever you want if you try hard enough. Back his first couple of seasons in the league Zion was better than Brown at that time, but not right now.
The tougher question is what about over the next say 5 seasons. It should be the prime of Zion's career for a player who for a short time was a dominant player in the league. But the reality is that we may never see that Zion again. This has similarities to Ja Morant (different issues but same questions). He also was a dominant player for a time but will he be one ever again? Maybe. I see Zion as having a better chance than Morant but I see it as the odds are against both.