For people who have some sort of writing practice (i.e. journaling, a blog, etc) know how beneficial it is to give words to your thoughts and actually express what you are thinking. It is liberating and so powerful.
When writing, it actually works best for the reader (not saying that there needs to be one) when the written word sounds like the author speaking about that topic. Through writing however, you might find that you want to use more precise and eloquent words (not for the purpose of being arrogant, making other people feel dumb or losing readers interest because they simply don't understand what you are talking about - especially important for industry language).
Not only will your writing practice effect that your mind is clearer and that you can actually express your thoughts and what you are thinking (because you already took the time to process the thoughts), it will also help you to bring across the point(s) you are trying to make.
So, not only is it best for you to write as you speak, you should also adapt to speak as you write and appreciate the beneficial loop writing provides you with for both outcomes.