This thread has brought up what I think is an interesting question. Your research clearly indicates that wool was uniformly the preferred material over various regions. Why do you think this occurred?
It boils down to efficiency of labor as well as practical use.
Leather gets wet: it stretches, takes quite a bit of time to dry and when it does dry, can get a bit stiff (BT seems to have less of the last problem)
Wool gets wet: It doesn't stretch, dries quickly and when it dries, it's the same as before.
Labor involved in getting deerhides, scraping/tanning them and sewing leggings was more than it took to getting deerhides (in the South) or beaver hides (in the North), giving them a scrape and then trading them for cloth. Not to mention that cloth is MUCH easier to work than leather.
Leather has little insulation value in cooler weather. Wool has excellent insulation value, even when wet.
Using the standard of trade for Fort Stanwix, which is an hour away from my house, as an example:
1762
"One stroud of 2 yards long {cost} Two beaver or three dressed buckskins."
So for the amount of deer it took to make 1 1/2 pairs of leggings, you got enough wool to make at least 3 pairs.
I find this interesting as I would have expected regional differences based on material availability and local cultures. Do you find regional variations in design or is that fairly uniform as well.
In my area of study (pre-1783 Great Lakes, Canada and the colonies), the descriptions are virtually identical. Flap about 4 fingers wide, seam along the outside of the leg, snug-fitting, ankle to a hand's width above the thigh.
NOTE: Later on in the South, you see a change in some places to a seam that runs along the front of the leg.
Mario