I have always gravitated toward Debian until recently. I run LXCs on proxmox and apparently Debian needs nesting enabled or else it takes around 30s to login. I think it's trying to access a system file when a user logs in that can't be accessed when nesting is disabled, and it waits to timeout before continuing with the login. Also, I have noticed that when running htop on Debian, it reports the total number of cores on my server, rather than the number of cores I have assigned to the container. Ubuntu doesn't have either of these problems - I can run it with nesting disabled (more secure) and still login without delay, and htop reports only the number of cores I have assigned to the container.

These are small issues, and there's probably a way to address them, but I haven't found any solutions yet. And when I just want to spin up a LXC quickly so I can work on an idea/pipeline/whatever, I'm finding myself going with the more frictionless option lately.

Edit to add: I run all of this headless, so I can't comment on GUI differences or anything like that