It really is a choice the writer makes. Stephen King is definitely a pantser...the starts off and knows not where the story goes. I am not sure, though, how much time he spends rewriting to fix plot holes, inconsistencies, blind alleys, etc. to produce a second draft.

Other writers can't write that way. They produce outlines so detailed that the actual writing is embellishment. Sometimes these writers are the opposite of writers like King...they start with the ending they want, and create a story that leads there.