Honestly, i think the best option, and also the easiest option if you want ubuntu server with desktop features is to run the command:
sudo apt-get install ubuntu-desktop
this way you can get the desktop environment, with the server application of ubuntu server. hope this helps somebody
i know this is an old thread but it was the first returned result when searching goole for the string "ubuntu server vs ubuntu desktop" so i imagine many people googling for this topic will find this thread.