I believe there is more truth in fiction than in non-fiction. Truth is not about reality—as in what is real and what is not. On that basis, non-fiction contains truth and fictions contains little or no truth.
Truth is about how things work in life. Usually these lessons get distilled into archetypal stories that demonstrate relationships that occur over and over again. Myths are a special kind of fiction that stands the test of time—centuries or even millenniums.
It is for this reason that the myth of God is so powerful. It contains truths that people have found to be true for millenniums. Other myths and “story tales” have lasted for centuries. They last because they tell stories that ring true in our lives or in our psyches. We are all Cinderella—lost and unloved, yet seeking; desiring love to complete our lives. We all wish for that completion, even if it is not completion (this is partially hyperbole, but you get the idea).
Fiction contains distillations of truths about relationships and meaning and the way the world works. Fiction also contains reality in it. I have learned much of what I know about physics from science fiction. Writers have to research works of fantasy just as much as they research non-fictional works. Most writers place a premium on credibility. They can not get readers to suspend disbelief without credibility.
As @drdoombot, showed us, fantasy (science fiction is a subgenre of fantasy) also allows us to speak about current events. Stories about meeting with aliens are about meeting with strange people or creatures. They can be about racism or bad wars or about the nature of metaphors for information. They can be about any issue that concerns the writer. If the story is about issues that also concern readers, and it has interesting things to say about these issues, then it is more likely to become a best seller.
I have always preferred fiction, perhaps because fiction sees deeper into the world. Non-fiction often bores me, because, so often, it just describes things (far to often in a boring way), instead of delving into the meaning of things. Fiction also forces writers to tell stories and stories are how we convey learning more effectively. We intuitively understand action and and conflict and purpose and journeys. Mere description does not provide that for us, and is less interesting because of it.
As always, there are exceptions to the above. Many people prefer non-fiction to fiction. They require “reality” in order to get into something. They don’t see the point of fiction. Maybe stories even bore them. For me, however, stories contain truths that can not appear in non-fiction, unless that non-fiction takes the form of a story.