Interview Question...?

I have an university interview during the next week, and I've just thought of another question. I expect to be asked to talk about a event that has recently happened with my chosen career, but I'm unsure what the interviewer will be looking for.

Will the interviewer be looking at HOW I am at talking about the event, or the subject matter itself?

Also, does it matter how big or small the incident/event is? I'm unsure whether to talk about a report commisioned by the national advisor a couple of years ago (the last one that was commisioned), or an incident that happened on the street more recently.