I would respectfully add a third, and possibly the best class of machine for this type of work. A harness stitcher, such as a used Randall or new Campbell. These machines were designed specifically for harness work, and Campbell has a lay-away plan I think. This is of course once you've done some hand stitching, decided that you want to go into production, and need a machine, perhaps you don't.
Other (used) considerations would be a Pearson #6, or Landis #1, I picked a Landis #1 up in great shape for $400, and it would do fine harness work all day long. But parts/needles etc are not as easy for these machines.