Surprisingly, this one is easy for me. It is hard in the NBA to find players that have that unquantifiable factor of ice water in their veins. With Fox, we saw it in high school, and college, and in his rookie season with the Kings. It's that leadership moxie and that "give me the ball and get out of my way I'm going to go in the game" mentality.
As far as skill sets go, if Giles is fully healthy and his high school game translates to the NBA, he can be a franchise changer. But the injury history gives me a great deal of pause.
Having a De'aaron Fox makes it possible to not have to find that superstar with the killer instinct. You can just surround that guy with great scores and great defenders that are not necessarily the cornerstone of the franchise. That can be highly undervalued but it's greatly important
TL;DR - Fox