I can understand the usefulness of loose dynamic clothing because it can move with a character's body. Conforming dresses look fine on a figure standing up, but don't often look natural in many other poses such as sitting or kneeling.

Bikinis tightly fit on the body, so I can't see much value in using dynamic cloth there. I suppose there might be some need in animation if breast morphs are moving them as part of the animation. A well-made bikini will have the same morphs as the base figure, so should have the same degree of movement. It's hard to understand where there might be something more useful by having a dynamic bikini.

Yet, DAZ is selling a dynamic bikini for Poser and DS, but the descriptions don't offer any advantages over conforming bikinis.

My visual indexes of Poser content are at http://www.sharecg.com/pf/rgagnon