It would depend on how you intend to finish the inside of the building, but I wouldn't run them in the gap regardless, too much chance of somebody running a screw or nail in from the outside.
Years ago when I worked for a guy that did alot of pole buildings, most we did were not intended to be insulated. We mounted the boxes to the face of the poles, ran conduit up to the bottom of the rafters and then ran the bare romex from there. Anything that ran below rafter level was done in conduit. This protected the wires where they were most likely to be damaged, but indeed did use a fair amount of extra wire, which some guys bitched about.
If you're finishing the inside, you can run the wires inside the wall following the same rules as any framed building, which means drilling the poles here and there, or run them in conduit on the surface.
