I don't agree: It's not because the developer answered, that it is by definition the most useful. Usefulness also depends on wording, sample code, and directing the real problem. I've read many interesting explanations from developers that actually didn't really address the problem, but explained why it existed. If the question is a solution for the problem, than the explanation about the internal engines is not what you're looking for.
The only criterion should be : which answer gives me the information I'm looking for in the most appropriate way. It might be useful though to wait with accepting an answer until you have a few answers, that avoids frustrations from switching the accepted answer around.
