Over the years, I've spent the bulk of my time with the Linux desktop using either GNOME or KDE. Both environments have grown over the years and each desktop has continued to expand its current user base.
The sleeper desktop environment – which I didn’t even considered years ago – has been XFCE. I've found that XFCE offers more robustness than say, LXDE, which lacks much of XFCE's polish in its default configuration. XFCE provides all the benefits one may have enjoyed in GNOME 2, but with a lightweight experience that makes it a hit on older computers.
MATE isn't a lightweight desktop
Before going further with comparing XFCE to GNOME 3 and KDE, I'd be doing this article a disservice by not touching on the MATE desktop as an option. Mate is considered to be the next incarnation of the GNOME 2 desktop, but it isn't marketed to be a fast, lightweight desktop. Instead, its goal is to be a comfortable, traditional desktop environment where users will feel right at home in using it.
By contrast, XFCE comes with a completely different goal set. XFCE offers users a lightweight, yet still visually appealing desktop experience. So to anyone who points out that MATE is also a "lightweight" desktop, it's not really targeting the lightweight desktop crowd. Regardless, both options can be dressed up to look quite attractive, with the right theme installed.
Theming the desktop
Upon a fresh installation, XFCE is arguably boring, and lacks any specific visual attractiveness to it. Don't get me wrong, it's still a good-looking desktop, but it tends to be rather vanilla in the eyes of most people new to this desktop environment.
Luckily installing a new theme to XFCE is a reasonably easy process. Simply find the XFCE theme that appeals to you, then extract the theme to the right directory. From here, XFCE comes with a great tool under Appearance to help you select the theme easily from a GUI. No other tools are required, and if you follow the directions linked above, it's quite simple for anyone who cares to try.
On the GNOME desktop, you would follow a similar approach. The key difference here is you must download and install the GNOME Tweak Tool first. Not a huge barrier by any means, but it's a valid oversight when you consider XFCE doesn't require a tweak tool to install and activate new desktop themes.
Under GNOME, after installing the Tweak tool described above, go ahead and make sure you have the User Themes extension installed. Like XFCE, you'll want to find and download the theme that most appeals to you personally. Now revisit the GNOME Tweak tool, clicking on Appearance option on the left side of the Tweak tool.
Next, look at the bottom of the page and then click on the file browse button to the right of Shell Theme. Browse to the zipped folder, click open. If the process was successful, you'll see an alert telling you it was installed without any problems. From here, simply use the pull down menu to select the theme you want to use. Like XFCE, the theme activation process is easy enough, however the need to download a non-included application to use a new theme leaves a lot to be desired.
Finally, there's the process of theming the KDE desktop. Like XFCE, there's no need to install extra tools to make it work. Quite frankly, this is one area where I feel XFCE has to give the win to KDE. Not only is installing themes in KDE accomplished entirely within the GUI, it's even possible to click on the "Get new themes" button and you can locate, view and install new themes automatically!
It should be noted however, that KDE is a more robust desktop environment than XFCE. Therefore, it's reasonable to see why the extra functionality might be missing from a desktop designed to be minimalist. Still, I must give KDE props for this awesome functionality.
XFCE offers painfully obvious navigation out of the box. Straight away, anyone who is used to a traditional Windows or GNOME 2/MATE desktop experience is going to be able to navigate around a new XFCE installation without any help. Adding applets to the panel is very obvious. As is locating installed applications, again, just use the launcher and click on the application desired.
With the exception of MATE and LXDE, no other desktop makes navigation this simple. What's even better is the fact that the control panel is very simple to use, which is a huge benefit to anyone new to the desktop environment.
If you prefer the older methods of using your desktop, GNOME isn't for you. With hot corners and no minimize button (by default), plus the different application layout method, it will take most newcomers some getting used to.