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Personally I like all of them.
PD, is a behemoth... I mean you can really get in there and cutomize your needs.
WF is very mainstream... great modules. Simple, easy to use.
To be honest I cant really choose between the two in this case... I mean if you have the chance to use them both I definitely reccommend doing so. Thats the only way you will know which modules you will want to use in a particular circumstance.