I have neither jacket, but have one that is very similar to the Mt. Hardware and 800 fill, though a little heavier. The hood provides better temp. range and the neck on the GD doesn't appear to have much fill at all. The thumb holes on the GD are something I never use, as liner gloves work better for me when my fingers are cold. I can't imagine why the 200+ price difference, but I know which one I'd be returning; fit being equal, of course.
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Charlie