Recently I switched from Xubuntu to Arch linux as my daily driver and I decided to give Gnome 3 a try over XFCE. While XFCE has served me well for many years, the development on XFCE is not as active as on Gnome 3 (unfortunately). For example, whereas Gnome 3 has been running on GTK3 for a while, XFCE is still in the process of being ported to GTK3. This means (among other things) that Gnome supports the Wayland display server protocol, whereas XFCE does not.
One of the things I’ve always liked about XFCE is the many customization options it presents to the user. This makes it a very flexible DE that can be customized to your needs. For example: as I spent a lot of time in the terminal I like the terminal output to take up as much screen estate as possible (where vertical screen estate is at a premium on a 1080p display). In case of the XFCE terminal emulator, you can choose to hide the window menu, the window borders, the window scroll bars and the window title bar. This saves screen estate which can be used to display ~two additional lines of code.