It's also a question of how one approaches writing: pansing vs plotting. Some authors, like Stephen King, swear by pansing and begin by forcing themselves to produce a certain number or words; whether it starts with character development or the plot, they exercise their powers of putting words on paper. Some authors, like J.K. Rowling, take a different approach and begin with sketching, diagraming, etc. I don't think the two are mutually exclusive, though.
Sometimes, even in the same piece of writing, I bounce back and forth between the two strategies.