I think there are two ways you could approach this: technical, and personal.
I would tailor my answer depending on what I thought the firm was looking for.
So, if this was HSF asking me a question, I'd definitely answer with something technical and explain in-depth my reasoning. That is where the points are going to be scored in this exercise.
If it were another firm who place a good weight on your personality, have some fun with it! But whatever you answer, you should be sure to go through your thought process and explain how you have come to the decision and reflect on it where necessary