I prefer the zippers face down, personally. I spoke with another TB owner during a layover in Atlanta; she mentioned that the zipper becomes "stiffer" as wear and tear rubs on the exposed teeth of the zipper. She had a lovely indigo/steel pilot with the teeth up; I had my beloved black/Iberian Aeronaut 45 (soon going to a new home and a cardinal WF with zipper face down to replace). The Aeronaut zippers were definitely smoother to operate than the Pilot's. But YMMV!