I agree with Vilas - both depth and breadth of knowledge is important.
As an instructor in the USAF and now check airman at my airline, I have never answered a students question with, "That's not important, you don't need to know that." The more insightful the question, the better the student.
The relevant question: "How do we make ourselves and our pilot group better?" This forum most certainly has made me a more knowledgeable pilot. I read replies to questions I would never have thought to ask.