I've tried nix-darwin a time or two in the past. Every few years when homebrew makes a "hostile" change and I get upset I consider trying it again (now most recently with changes to gatekeeper). I think I'll get to doing so in the next year or so.

But I think just in fairness, the comparison here for flakes should be to Homebrew bundles. My packages are managed in a bundle: https://github.com/Julian/dotfiles/blob/main/Brewfile and then locked by a lockfile: https://github.com/Julian/dotfiles/blob/main/Brewfile.lock.j... and installing is just `brew bundle install`. All native Homebrew functionality. In practice I have never had an issue with non-reproducible builds across my machines (partly because the tendency on macOS is to run the latest versions of things and stay up to date).

(But again I do find nix-darwin interesting to try for other reasons.)