Casey Liss wrote about why you should use DuckDuckGo.
Like Casey, I switched to DuckDuckGo when I upgraded to iOS 8. DuckDuckGo promises not to track you and that is a huge deciding factor for me. So when Apple added it as one of the built-in search options, it became my default search engine.
Of course, there are some situations where it loses out to Google. It uses a different algorithm and gives you the best results, whereas Google gives you the most popular one. And if you are signs into Google, it actually takes your browsing history into consideration and ranks sites that you frequent higher.
Google Images is still superior, and I find myself going back to it when I need to find images.
With DuckDuckGo’s !bang operators, you can easily fallback on Google search with !g and Google Images with !i.