What is the best search engine to use with Safari?

Best is subjective, and everybody has their opinion. Personally, I use DuckDuckGo for 90% of my searches in Safari, there are some times, I need google to find what I am looking for. I don't use Yahoo or bing.

You will get as many opinions as the people giving them. It’s up to you. Under Safari-> Preferences->Search you have four choices for the default search engine to use. Try each one for a while and decide which one you like the best.

Best?

I use DDG.