The looped metal stuff is called spiral steel. It bends forward and backwards like the regular spring steel does but it also bends side to side. Therefore it is meant for different applications. Some people who make corsets use the sprial steel in the sides of the corset only to allow for a little better movement. It could be used everywhere, however, it is heavier than the regular spring steel. Also, the spiral steel only comes in one width (as far as I know) so it is limited in that nature. Spiral steel can be bought by the metre/yard and is a little easier for the home sewer to cut and re-tip although it requires some heavy duty wire cutters to do the job. Spring steel is much harder to cut, although it's still doable. Spiral steel fits the bill well when you need an unsual length. 99 percent of the time I stick with spring steet but I always have spiral on hand. I totally agree with your sister, JonnyAmateur....making a Victorian corset with with all that boning would weigh a TON if you used spiral steel!