At the Willamette Writers Conference workshop I attended with Larry Brooks, he talked about the spectrum of advance work that novelists do. Some people are what he called "planners" (and he was one). They map out the whole strategy, the chapters, the major and minor characters, the major incidents and plot twists. They spend a lot of time on this and then write from this outline. Brooks says this saves a lot of time because you sort out the difficulties and the weaknesses beforehand and don't have to do so much rewriting.
On the other end of the spectrum are those who write by the seat of their pants (pantsers), who, he said with some disdain, claim their characters talk to them. I'm one of these. I'm probably not completely on the liberal, loose end of the spectrum. I do some serious consideration between writing sessions to sort out what comes next, rather than sitting down with no plan at all in mind. Right now I know what's going to happen in the next two and maybe three of my chapters and definitely that we are coming to the dramatic end of Act I. But I don't know "who done it" in my mystery, I don't know if my heroine will end up with any of the leading men, I don't even know if she'll be alive at the end of the book.
It's more interesting to me to let it unfold. If I'd worked the original idea to its logical conclusion in a plan, I might never have come up with the story that I've got going now.
I don't think one way is more valuable than the other, or leads to better writing. And I don't think Brooks was intimating that that was true. But I do think my way's less work and more fun.