MacGill Modern is a Lochcarron weave in 10 and 16 oz, while MacGill Ancient is a Lochcarron weave in 16 oz. They make great quality tartan, one of the "cadillac's" of the industry, not cheap but probably worth the bit of extra cost. At least it is not a special weave, which can be far more expensive. Biggest issue is whether or not it is in stock somewhere.

Good luck. Hope this info helps.

j