Your answer to this question tells the interviewer something about how you view the world. What is more important for judging a person's fitness for a job - his specific technical knowledge or his general behavior and personality? Either one is a possibility. You may view a complete command of job-related technical detail as most important. No one can say this is wrong, but then you have to be prepared to deal with a wide range of personalities, some quite difficult. If you choose behavior/personality as the best differentiator between potential success and failure in a job, then you may need to be prepared to deal with a wider range of technical capability or knowledge.