[zamalek]

Distros seem to be having a hard time updating glibc, and there are known vulnerabilities with the pinned version of most of them. Musl/Alpine doesn't have that problem, because it doesn't use glibc.

Ubuntu comes with snaps. If you don't use snaps, they are consuming a not insignificant portion of boot time. Use Debian if you need something glib-based. If you must use Ubuntu, make sure you are using slim: you don't need manpages etc. in a production container.

Overall boot time is affected by image size, because your cluster has to download that image from $SERVER. Alpine is smaller than most, scratch is even better (if you can pull it off). Building containers with Nix can result in stupidly small images.

Its not clear-cut, but hopefully that helps you make a choice.