From ratpoison to Unity, I must have tried just about every Linux desktop environment available. The best Linux desktop, in my view: my main computer continues to run KDE's Plasma. No other alternative can match its design philosophy, configurability, or its innovations on the classical desktop.
Nor am I alone in my preferences. At a time when the Linux desktop offers six main alternatives (Cinnamon, GNOME, KDE Plasma, LXDE, Mate, Unity and Xfce), KDE Plasma consistently tops reader polls with an average of 35-40 percent. In such a diverse market, these figures indicate a broad appeal that other Linux desktop alternatives can't match.
I believe that one of the main reasons for this appeal is the KDE design philosophy. GNOME and Unity may offer a more aesthetic-looking default, but only at the cost of simplifying both the desktop and the utilities in the name of reducing clutter.
By contrast, KDE goes to the opposite extreme. KDE applications typically include every function you can imagine. Sometimes, they can take a version or two to organize the menus in a meaningful way, but applications like Amarok, K3B, or digiKam go far beyond the most common use cases. When you run into problems with them, they usually offer solutions.
Moreover, with KDE applications, you have the opportunity to learn. GNOME and Unity designs may be quicker for new users to pick up, but KDE applications give users the opportunity to explore and learn new techniques and options. While the apps for other desktops leave users perpetually at novice levels, the KDE equivalents offer the chance to add to your expertise.
What I call the completist philosophy of KDE is especially obvious when you start to customize.
All Linux desktops give you options for changing wallpaper and fonts. However, none match the options available in Plasma. With eight hot spots, several dozen desktop effects (most of which are practical rather than eye candy), and the ability to change the behavior of individual windows, Plasma has a strong claim to being the most customizable of all the Linux desktops. You can even swap out the interface itself for another format.
In fact, at a time when many alternatives have banished icons from the desktop, immobilized the panel, and eliminated panel applets, Plasma not only makes provisions for all three, but supports an extensive system of widgets to place on the desktop. What's more, these tools are not just the minor utilities that are part of GNOME 2 and Mate, but also additional pieces of functionality, such as alternative menus and task bars and virtual keyboards for accessibility.
Best of all, you can customize as many or as few of these features as you wish. If all you want is the standard cosmetic alternations to the Linux desktop, nothing forces you to go any further. But, if you do want to explore, these alternatives are always there, awaiting your explorations.
Probably, what I like best about Plasma is the way that it combines the classic desktop with enhancements that can improve your work-flow.
Those who want a classical Linux desktop of the type offered by Mate or Xfce can quickly set one up, although the procedure in KDE is somewhat different. Yet, if you want more you can easily add more.
Instead of being stuck with one set of icons, you can use the Folder View widget to add several to the desk, or else swap the display on the desktop with just a few clicks. Alternatively, you can place different icons on each virtual workspace. All these choices mean that, instead of a generalized desktop or an impossibly cluttered one, you can have specialized desktops for different tasks or projects.