I usually use this story of blind men describing an elephant to explain difference between #FreeSoftware and #OpenSource.
https://en.wikipedia.org/wiki/Blind_men_and_an_elephant
A very widespread misunderstanding equates #copyleft with #FreeSoftware and permissive licenses with #OpenSource.
In almost all practical cases you are referring to the same software.
The difference is what you focus on and this focus difference gives you different conclusions. So I focus on 4 freedoms for every user ie, copyleft Free Software.