[kjeetgill]

I wish you weren't downvoted, this is exactly right.

The nice thing about S2 is that is subdivides cleanly: A square can be composed of smaller squares while hexagons can't be. This property makes S2 much more broadly useful for a bigger range of applications.

In H3, each hierarchical level of hexagon doesn't fit cleanly in the one below. For Uber's uses, this is acceptable because hexagons have more uniform adjacency but the "zoom in and out" math is pretty gnarly.

But even S2 had the funkyness of first mapping a sphere to a cube. They're both fairly interesting to read up on.