Debian is (rightfully) known for being lightweight and very stable. Particularly with older hardware, while still being quite compatible with newer hardware. Their long-running release cycles tend to not break whenever updates do roll out. Ubuntu is Debian based as well, its focus however is on user friendliness and usability, especially on the GUI front. Ubuntu server is perfectly fine, but it’s heavy handed compared to a minimal Debian installation with just a handful of packages selected purposefully by the user for the task it is intended for. There have also been more vocal complaints about whatever Canonical is trying to do with snaps/snap store.

Most beginners with Linux I would more encourage to try Debian for its stability and speed because it’s a great platform to learn Linux on as well as experiment with whatever goal they have by way of packages and projects available all over the open source side of the web.