Let me be the first to point out that the format for your speaking may not be your choice. Organizers may need to use one setup for many speakers, or may prefer a less or more formal atmosphere, and they're calling the shots. But savvy speakers can add format to their negotiations with organizers. Here are some factors to consider:
- Why are they offering an interview format? This is a great question for you to ask the organizers. You may learn that it's the only format available, that they want a more spontaneous presentation, or some other factor with which you can negotiate. But ask first.
- How much preparation do you want to do? Preparing a formal speech or talk is a lot of work. That's why you so often see celebrities doing Q&A format on stage--the organizers can then make the invitation easier to accept, because the famous person need not prepare as much. I'd recommend preparation for an interview format as well as a formal speech, but it's a different level of prep.
- Do you want to look in control or able to take the heat? To be honest, most interviews of this type throw softball questions--easy ones that let you shine. But if you get a fair questioner with at least some tough questions, it's an opportunity for you to demonstrate that you're able to take the heat. A formal speech, no interviewer involved, lets you have a bit more control of the presentation.
- How much audience interaction do you want? Oddly enough, it's the formal speech that gives you more options for audience interaction. You can speak to the audience, ask questions of them, open yourself up to their questions. In an interview, the interviewer is, in fact, a barrier between you and the audience, most of the time.
- How will sitting affect your performance? Most people lose energy when they sit, and you have more options for movement if you stand, even if you're working with a lectern. Read my 6 reasons to stand when you speak for more points to ponder. You may be able to negotiate standing during an on-stage interview if sitting would drain your energy or otherwise affect your performance.
- Will this format show you to best advantage? If you're no good on your feet or in interviews, or the reverse, no good at formal talks, you need to consider how you'll be seen in this format. On the other hand, with practice, you might be able to expand your range by trying a new format.