Catmull-clark and simple

Hello! In modifiers both subsurface and multiresolution have two options that are catmull-clark and simple. In multiresolution it is preferable to use the catmull-clark by the smoothed mesh. What is appropriate when using the simple option?
It will be something flatter because the simple form of the object is original. Will the work on it add other modifiers?
What could you explain to me?

Simple subsurf is useful if you want to do things like displace geometry on architectural meshes, ground planes, and other types of detail where the smoothing is unwanted (via the displace modifier or Cycles microdisplacement).

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