There certainly are advantages to being master of a super vocabulary. Among other tools, we use words when we think. The better our vocabulary, the better we can express our thoughts to others and even to ourselves.
It isn’t enough, however, to have a good vocabulary. We need to know how to use it most appropriately. Used in the wrong way, it can cause more harm than good.
When you write a professional document, there is no doubt that you need to use the very best words you can muster to express your ideas. The more accurate the words you use, the clearer will your ideas be expressed. Use a dictionary and a thesaurus extensively if you need to check the exact meanings of problem words. Even one word inappropriately used can turn your carefully crafted paper to a source of ridicule.
Be careful how you use words in casual conversations with others. Be considerate of the capabilities of other persons. Avoid using words which you suspect your listeners may not be familiar with. The other persons may deem your doing this an attempt to display a superior intellect. Use simpler words to express your thoughts even if they aren’t exactly the ones you would use in a formal document.
With another individual who is easily your equal in word knowledge, or even better gifted, it’s OK to use the words that express your ideas most elegantly. But, even here, it would not be a good idea to use unusual or esoteric words where simpler ones would suffice just as well. Let those, who are trying to impress others, use the more arcane words.