Search Engine Journal takes a look at how DuckDuckGo compares to Google. The summary is pretty much what I would expect from this type of comparison:
Anyone who is passionate about privacy would likely lean toward – and prefer – DuckDuckGo solely for its strong privacy policies but also since it is a better-than-average search engine trying to do right for the people. And it does a strong job in achieving that.
That doesn’t change the fact that, if you can’t find an answer on DuckDuckGo, you’re going to go to Google to find it. And you will find it there.