IT Manager Question:

You want to tailor your answer to match the job or their corporate culture. For example, if you're interviewing to be an airline pilot, don't tell the interviewer that you like to sleep on things before making a decision.
Or, if you're interviewing for a medical position, you don't want to come across as one who makes decisions on a hunch.
Before I make any kind of important decision, I first consider all the surrounding facts, possible outcomes and the desired goal. I won't hesitate to seek an outside opinion and I generally do, but I am the one who makes the ultimate decision.