I always have preferred bare feet, but this is probably because I have a foot fetish, and like feet in addition to tickle. I like how when the lee is barefoot, you can really see a closeup of the toes scrunching, pointing, or wiggling, if you pay attention. With stockings on the view seems to be obscured as to exactly what the toes are doing. As to which is more ticklish for the lee, I've heard conflicting stories. Some lees have told me stockings is worse, others say bare. I think it depends on the tickler, how they tickle, how ticklish the lee is, and the sensitivity of her feet.
Mitch