Couple of things about WW. It only comes with support for the figures that are included in Poser. Support files for M4 and V4 are sold separately by PhilC on his site. You must have both to convert from one figure to another. The likely reason you couldn't create the morphed version is you don't have one or both of the required support files installed.

You get WW with Poser. The Crossdresser app if free. The main difference between them is that WW requires support files for both figures. Xdresser requires only the license for the figure you are converting to. So it's mainly a matter of price and which app you prefer. Both will convert clothing. The quality of the conversion can vary with any number of factors.