I can't find the information that show the exact numerical difference that a Gargoyle character has over human and elves, but I do know that having it is good. If you are adding the 5th property to an item and are near the 500 weight mark, you will probably lose less ingredients if you are Gargoyle and are at the Queen's forge. Of course, this too is random. If I am remembering right, I seem to recall it being about 5% bonus.