Generally setting up a server is the same throughout the versions. The only difference may be some dependencies that are needed or extra databases to execute.
The reason those versions are most released is generally because that is what has always been readily available to the public. The higher version you go, the less sources you will see solely because people don't want to release their server files that they updated, from version to version, to the public. To be capable of that, not to mention the journey of coding AFTER updating, takes a lot of dedication and time. Most sources released are just variations of another, with minimal changes that honestly make it no different from another. Only a few sources are unique enough to be considered a genuine new release. I will also recommend, if you plan on making your own server, update on your own as it will not only help you understand your own source more, but will allow you to control the quality of the source as well. Most high version sources released are either poorly done, or no where near stable / complete.
