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It's still possible to crease parts of your mesh when using a good implemented subdivision, so the modeler can decide what should be smoothed. Afterwards, the process is automatic.

IMO this is the single most important reason, why Catmull-Clark can be generally considered a very good idea to have in a program like DS and Poser, but Poser's smoothing is not: practical any 3d modeling program has a CC subdivision built in, but very few have Poser-smoothing built in (i do not know of any, do you?). It does not matter that much, if any of those smoothing variants are better implemented than the other. it is simply the fact, that with CC, the modeler can decide what should be smoothed, simply because the modeling program supports it, too. Poser's subdivision can be as good as it wants, as long you cannot effectively build models for it because your modeling application does not support it, you always will get inferior results with it in the end.