Currently the 3 main areas that make DDG specific are :
2. 0-click info
3. less spam in the search results
The first one is very well explained on this page
, the second is quite obvious if you do a random search, however the last one can be a bit obscure.
A good way to demonstrate this could be to add an example of query that shows a lot of ads on Google, and the same query done on Duck Duck Go, to show how the result page is cleaner.
Because some users are using ad-blocking in their browser, and totally forget that Google SERPs are full of ads, also show another page where there is obvious SEO spam in the results.
I also think it would be great to explain a bit that there is a DDG specific technology to detect and remove spam in the results, without giving too much details of course. I actually learned about it in the Youtube interview posted on this forum, and it does not seem to be documented on the site.