I've not made alot of these. I poured over several chairs at the Philadelphia Museum of Art and they were later than QA. On those chairs, I saw no file or rasp marks on lower legs. Certainly none on the feet or knuckles. File or rasp marks do appear on chair backs. Areas behind the knees appear to have been cut quickly with a tight gouge. Didn't see file marks there.
If I were to guess about period techniques, especially those of London or Philadelphia chairmakers (and these may very well be different from New England chair makers) I would guess they made great use of gouges, and possibly draw knives or spoke shaves. So based on what I saw, edge tools looked like they trumped abrading tools.
Based on my limited experience, as great as scrapers and files are, none equal a sharp gouge for speed or the surface left behind. Facets on Philadelphia balls are fairly common. Didn't see facets on legs. Could be that scrapers were used there or wear and refinishings removed original facets.
Generally, i get the sense that New England builders sought smoother more reflective carved surfaces. i think this was an esthetic/artisitic choice. Perhaps for esthetic reasons or perhaps for economic reasons, London and Philadelphia sculptural elements seem to be a little punchier, faceted, sometimes with punched (stippled) "grounds" and generally have a greater distinction between reflective surfaces and non-reflective surfaces (which I think is a baroque concept which may even include a chiaroscuro sensibility).
I don't mean to overly exhalt what we and our woodworking ancestors do/did, but I think this specific issue (how to shape a cab leg) really crosses the art/craft line. While I'm typically happy with the "Rude Mechanick" label (and tee shirt), one really has to own all this art history stuff to be successful with this specific sort of work.
adam
Links
http://en.wikipedia.org/wiki/Chiaroscuro