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You can easily see the "vanity" sizing of the modern era. 6/8 is the new 12. Personally, I prefer the bust size as pattern size as it makes it simple to find the correct size pattern. Notice that the waist of the vintage patterns allows 2" more than a modern pattern and the hips allow an extra 1"+ in the more mature lady's size. The younger lady would get an extra 1"+ in the waist and 1/2" in the hip. In other words, if you've got curves, a vintage pattern is your best friend because there's a lot less monkeying around that needs to be done to get it to fit.
This is why I don't sweat garment and pattern sizing any more.