I don’t think there’s a very clear answer. They’re the consensus top 2 in the league, similar age, career achievements and late bloomers. Both relatively injury free so far though Jokic is more available, both seem intent on staying all or most of their careers with their draft team.
Personally, I think it’s harder to build a team around Giannis you’re going to need people to compliment his weaknesses in shooting, free throws and late-game situations. Jokic dosen’t need as specific tailoring of teammates to his skills so your team might be more consistent through roster transitions. I guess you could knock Joker down for his defense but finding a power forward like Gordon who can cover up a bit on defense is easier than finding multiple good shooters.
Secondly, Joker’s game atleast appears like it’ll age better because it’s more IQ and finesse than athleticism. That might change if Giannis develops his game with age like Lebron did but it’s a less certain bet than Jokic.
Jokic, best scorer in the league, best passer in the league, elevates teammates with his spacing away from the rim and wins in dominant fashion. Giannis never put a complete dominant run together. Was outplayed by KD when he won and only won because he injured Kyrie with a shameful play not allowing him to land.