I’ll try not to be opinionated, but starting an app inside Ubuntu typically has 50+ processes.
In most cases with Alpine-based containers, the only process is the one that you actually want to run.
Add to that that modern Ubuntu uses systemd which greatly exhausts the system’s inotify limits, so running 3-4 Ubuntu-containers can easily kill a systems ability to use inotify at all, across containers and the host system. Causing all kind of fun issues, I assure you.
In most cases with Alpine-based containers, the only process is the one that you actually want to run.
Add to that that modern Ubuntu uses systemd which greatly exhausts the system’s inotify limits, so running 3-4 Ubuntu-containers can easily kill a systems ability to use inotify at all, across containers and the host system. Causing all kind of fun issues, I assure you.
So the cost is not just about disk-space.
Disclaimer: more experience with LXC than Docker.