Personally, I think it depends on the sitch. Something immutable would probably be the better go for people coming from Windows and would help with IT costs since all systems would be, at their base, the same. No one is going to accidentally install something that breaks their system. And the main drawback of immutability (less control over the system) wouldn't be a problem because people shouldn't be installing things on government systems that are outside the scope of their job.

EDIT: In a sentence: a good distro is one that's good for your organization.

Basically everyone in the community agrees that Mint, Ubuntu and Fedora are the best choices for new users. Mint and Ubuntu are pretty similar, so they don't require separate maintenance effort, and supporting Fedora is not that hard, if you already support RHEL, CentOS or another rpm-based distro (which are pretty common in the enterprise space). For all the desktop applications, Flatpak exists and is agreed on as the standard format by most of the desktop Linux community.