So in general, what do you think are the differences between "short fiction writer's mind" and "novel writer's mind" based on your experiences as a prolific generator of both?
My answer (edited for clarity in response to dthon's comment):
I think that short fiction writers have to see around corners very quickly. They get invested in the telling detail, in pithy exposition, and in a certain very tightly structured narrative pattern.
Novel writers are not only able to be looser and more expansive, to some degree they must be so. A novel has to have rhythm. Where a short story can be a heads-down sprint, in a novel you need to digress, let the reader (and character) breathe, provide wide angle views of the world and the story.
It's like the difference between growing a bonsai and planting a forest. Millimeters of wire might be critical in a bonsai. If you have 5,000 Douglas fir saplings, their spacing and positioning isn't nearly as critical. Except when it is, of course.