I have both Ubuntu 14.04 and Xubuntu 16.04 installed on one of my older desktops.
While both work fine, I experience screen tearing while dragging windows around in Xubuntu. However, I do not experience it on Ubuntu.
It is using the motherboard's built-in AMD graphics chip.
Note: This exact situation also holds true for my main desktop with a GTX650 graphics card...
At this point, I'm thinking it has something to do with Untiy being a 3D DE, and XFCE being a 2D DE...