The problem I have with Nix is that it adds a lot of abstraction/complexity on top of everything. This is fine for power users, but I don't see it ever being used by anyone else. Silverblue also imposes some additional complexity, but it's way closer to vanilla Linux than Nix is, and I believe the usability aspect of it is limited mostly by flatpak. I have used both quite substantially, and they both are good solutions. I love how easily I can reproduce my system in Nix from just a config file, and the ability to nix copy (with the entire dependency tree) to another Nix system is awesome. But I personally think Silverblue is an easier sell to most people.