Google may provide results that are more relevant based on you looking for someone you are in a community with, whose pages you are searching for are relevant based on searches you have made.
This specifically relies on keeping information about you that DDG won't.
Adblock, do not track, ghostery, privacy badger, and Google's opt-out cookie are among the tools I'm aware of which may affect this behavior. It's complicated.
(1) Ad for Christianity
(2) GitHub Profile
(3) Twitter Profile
When I search the same thing on DuckDuckGo, the first three results are:
(1) Twitter Profile
(2) LinkedIn Profile
(3) GitHub Profile
I definitely think that the first couple of results on DuckDuckGo are as useful as those produced by Google, if not more so.