Former Google engineer Jake Voytko compared Google and DuckDuckGo's search results and thought that DuckDuckGo was good enough for daily use.
DuckDuckGo is a search engine that emphasizes privacy. It does not customize search results for users and does not track users.
Voytko's test shows that results that you can't find on DuckDuckGo would also not appear on Google.
However, in some areas, Google still maintains a strong advantage over DuckDuckGo. This includes product search and local search, and there are relatively rare issues where Google still returns useful results, and DuckDuckGo may find nothing.
Here is his full analysis: Link.