Besides z being much faster (looking through a sorted list of directories visited instead of recursively walking from the current directory) your snippet looks from the cwd

This is a fair point. I usually only "jump" from directories that have at most 500k files, and the median is way closer to ~500 files.

Even in the worst cases, at least with my i7 NUC and using fd instead of find, it's less than 500ms to load the entire list into fzf.

Yep, that's fair. I use fzf along with z. I use z usually to switch projects (and I work in Go, so many are in GOPATH and annoying to CD to manually) but I use fzf both inside and outside of vim to open individual files.

    I personally find that fzf is better because I can 
    see where I'm going to end up before I accept the
    operation. 

I agree that's a must-have feature. Luckily z does it as well.

Type `z foo` and hit tab.

If there's a single match, "foo" will be expanded in place to the proper path.

If there are multiple matches, you can choose from a list of paths.

So, no mystery navigation (unless you want it) -- you can always see where you're going.