PDMS is a realy good tool for Plant design. But much more older then Plant 3d, so more experience and better functions. Pdms uses isogen for isometric drawings, so you can config all what you want in the option file (if you know what to do), In Plant 3D you have a lot of Availabilities to change things in the Iso style. But the Iso output ist not the same as in pdms. Further it needs a lot of time to get the same result.