In this short essay, Bacon is examining reasons why, in his opinion, people tell lies instead of the truth. In the line you cite, Bacon argues that people like likes better because lies embellish the truth and make it prettier and more palatable.
Truth, says Bacon, is like a pearl because a pearl only looks good in the daylight. A diamond, by contrast, can look good in many sorts of lights. What he means by this is that the truth is bare and plain and is only palatable in limited circumstances. Lies, on the other hand, are fancier and can seem beautiful in many different circumstances.
Truth is therefore less valuable to most people because it does not really dress up and/or hide reality. People prefer lies because they make things look better than they really are.