When we started out, we were short on time and thought of using either whichever covers most of our target user base. Zopfli works everywhere whereas Brotli is not supported everywhere. Also, Nginx does not support Brotli out of the box and had to be compiled. Since there were some complexities as well, we went ahead with Zopfli only.

Now that we have more time, we have the luxury to setup infrastructure for serving both Zopfli and Brotli. Perhaps one of the next steps for us to make our website even faster.