Your main character needs an inner and an outer problem. The outer problem is the physical action in the book—what we call plot. The inner problem is the character’s emotional journey through the book—what we call story.
When action happens (the plot) the character reacts (story). Which is more important?
It’s your book, you decide. But Joseph Wambaugh, the grand master of the police novel, had a clear preference: “It’s not how the cops work on the case, it’s how the case works on the cops.”