Ubuntu Server comes with a bunch of nice quality-of-life improvements that make using it more pleasant than using stock Debian, and you get the predictability of Ubuntu's standardized release cadence (a new release every 6 months on the dot, alongside longer-lived LTS versions).
I have to say, none of these are benefits for productive use. You may want long-term stability out of a release, which is IMHO where Debian shines more. They provide much longer support times than what a Ubuntu LTS offers.
The latest and greatest package is not so much beneficial in production, and e.g. with containers you do not even have to bother much about it since all you probably care for is kernel and container runtime updates.
What I still would be interested in though is if there is any technical benefit from Ubuntu server? Something which is not easily resolved by configuration management or a simple "apt-get install"?
Little things. UFW included by default, so you can set up a firewall without having to wrestle with iptables. do-release-upgrade to handle upgrades, instead of having to work through a list of release notes each time. Nothing earth-shaking, just things that sand down some of Debian’s rougher edges.
Not speaking for the parent, but I much prefer Ubuntu over Debian in this context for the sake of the wider variety of packages from official repos that aren't a few versions behind by default.