My thoughts for what they're worth - feet (my feet in any case) look better bare than in nylons, legs (my legs at any rate) look better in nylons than bare. Since sandals are there to show off my feet, I wear sandals barefoot during the summer when my legs and feet are tanned, and make sure I have taken good care of my feet and nails.
In winter, for business, or whenever else I feel like courts instead of sandals (which, frankly, is most of the time) I almost always wear stockings (or very occasionally hose). Probably the only exception is with brown or navy courts which I think look good with bare legs if they're tanned.
With boots, it depends very much on rest of the outfit, again stockings with a longer skirt, bare legs with a mini
