Rear bike stand: 2 points of contact vs 1
A single-tube clamp has to be fairly tight to prevent rotation, especially if the bike is heavily/unevenly loaded.  A double-tube clamp doesn't have to be as tight.  Whether this is enough to allow you to use the double-tube version on fragile materials is another matter.

The fit of the double version has to be much more precise. With some frames it just won't work.  I wouldn't be confident about getting it to fit with rear disk brakes.