I would currently take him over Kornet without really thinking twice.
You probably should, Kornet is at least an NBA benchwarmer. Queta might eventually be more, but right now he's a prospect that fouls too much to actually play any minutes
The problem with Kornet is that, despite his height, he gets pushed around a lot and lacks agility, strength, and lift. I get that he understands the system and has some unique skills, but we already have a much much better version of him in Porzingis. What we need is a better version of what Queta is right now, and it's entirely possible he can grow into that role relatively soon.
Kornet will get the early opportunities, but I would love one of Queta or Gabriel to seize their opportunity and become a viable rotation player.