Recs.
Updated
Xfce is a low resource user friendly desktop environment created for UNIX-like operating systems.
SpecsUpdate
Pros
Pro A true UNIX Desktop Environment
Xfce adheres to the UNIX philosophy, which means it strives for being modular, minimal and expandable. This makes it very much customizable. You can make it as minimal as you want and as heavyweight as you want depending on the features and modules/plugins you use.
Pro Window manager (XFWM) is a compositing WM by default
By having a compositing WM as the default WM makes way for a lot of visual tweaks and tricks that can and do make Xfce look great. You can adjust the transparency, shadows, borders, etc. and many other advanced tweaks are also available.
Pro Adheres to standards
A priority of Xfce is adherence to standards, specifically those defined at freedesktop.org allowing for interoperability and shared technology for X Window System desktops. This interoperability is particularly significant for users looking to, e.g., run alternative window managers.
Cons
Con Screen tearing issues
The built-in compositor for Xfce does not handle VSync, meaning that it does not address screen tearing for those with Intel integrated graphics. A third party solution will have to be used for those that do want VSync such as using Nvidia proprietary drivers to handle VSync or installing a third party compositor such as Compton.
Con Missing some basic functionality for a desktop environment
Xfce is missing essential functionality like a file-archiver or a polkit-client, so you have to find alternatives for those applications (eg: by stealing them from MATE or GNOME, however this adds additional dependencies that will bloat Xfce).