I realize that all DE's are there "for a reason".. I never said that there should be that is the best at everything.Different desktop environments use different utilities. A desktop environment is not some kind of desktop theme. The file managers will be different, So, will the web browsers, the email clients, and so on. The developers of each environment have their own ideas of what a desktop should look like and how a desktop should work.
There are big differences between Ubuntu, Kubuntu, Lubuntu and Xubuntu outside of the choice of wallpapers. But then again, every computer operating system has to do similar things. They just do it slightly different.
To learn from this exercise you should be comparing the thinking behind the development of the different desktop environments. Ask yourself why did the developers of KDE, Gnome, Xfce, and LXDE decide to spend their time and resources to develop these environments? What need did they see that needed to be filled? Why did they want something different?
All I want to achieve, is to run a simple experiment in order ro see which one may be more suited for everyday use.