One of the great things about being honest and genuine when you're dealing with people is that you will attract like minded people to you. Like attracts like.
When the people you attract are of a like mind, you will get along better and all of your dealings will go more smoothly.
This of course makes your work and life much easier. And a person who enjoys their work is much more productive.
Maybe you could get a few more customers or clients, at least in the beginning, by not being yourself, by not being selective in who you work with and by making exaggerated claims. But these types of practices will come back to bite you in the end. More stress, more problems and a bad reputation will be the end result.
YOU are your brand.