From my research, it appears the big differences are that the 2017 models come with LG's latest OS installed (WebOS 3.5 vs WebOS 3.0). LG has also worked some magic on the video processing too. They are now able to get more detail in the very darkest portions of an image, where the 2016 models would sign off on the darkest details earlier & just represent them as total black. Lastly, they able to tweak the light output on the panels to improve overall brightness, which was a common complaint of the 2016 models that were installed in fairly bright rooms from what I have heard.
Thanks. Hope this helps.