Really, basically every server I see is either Ubuntu or Centos. Very few Debian. With containers is different, who packaged the container for a given service wins. Example: Elastic uses Debian for their docker images on docker hub.
See also the results of this survey https://brashear.me/blog/2015/08/24/results-of-the-2015-slas...
It begins to be old but this section is telling "Which Linux distribution do you primarily use on your server computers?"
Distro #resp %resp prev year
Ubuntu 633 34% 27%
Debian 539 29% 31%
CentOS 214 12% 15%
...