Some presentations win your business (or a job or promotion) others do not.
When it is the time to shine, you want to be "over prepared" and give your audience a clear message. Those two goals most of the time contradict themselves where "over prepared" becomes synonym with too much information and "clear message" becomes clutter of data in one slide.
Investing in someone helping you to create a presentation can seem conter-intuitive at first, because you know the topic the best, but I found (and psycology research agrees) that outside help gives propective and supports better your message.
Executive/ board presentation