If your infrastructure doesn't use landscape, kernel hot patching, JuJu or similar Canonical technology, or doesn't have its own Snap storefront, there's no need to install Ubuntu. Rest is just momentum.

Debian used to move a bit slow in terms of userspace, and that's true, but for servers, that's a non-issue for the last 20 years or so (from my experience).

On the Desktop side, Fedora and Ubuntu moves faster on the userspace front, but if your system is behind a NAT, and you know what you're doing, Debian Testing is just as good, more stable and it's rolling (except when it's feature freeze, but a stable workhorse is better than a shiny but breaking one).

Debian allows me to sleep well at night, provides guaranteed updates, and works rock solid all-round, so I won't be touching Ubuntu for the foreseeable future. Esp, with controversial choices like uutils, etc.