If I am honest, I spend 90% of my time in a terminal, browser or editor (which is also in a terminal), so give me a system that allows me to easily install my most beloved programs via command line and handy binary packages, a system that is reasonably stable, runs on most hardware, and that has a big community and a lot of documentation, sounds like a good deal actually.
What I originally thought about were systems like NixOS (for serious development), or something more minimalistic that offers greater control like Slackware, a *BSD (Jails, byhyve, dtrace(!)), or even just Debian (less flashy, more stable and robust).
Xubuntu is medium light for me and is fast. Previously I had only fluxbox on Kubuntu for the KDE apps which was extremely fast but with bugs in fluxbox I switched.
When you spend all your time at a prompt you don't really care about unity vs cinnamon vs anything else.
Debian is stable and has fantastic package management, and Ubuntu builds on that with a vibrant community and wide support. For these users, Ubuntu 'just works' and lets them get on with what they want to do. It's about as simple as that.