Printing directly to PDF is the same as printing a PostScript File and convert it to the Distiller. It is a shortcut via a library, but does the very same.
Why not using PostScript?
Look here these discussions:
Images turn greyscale when saving Postscript/PDF or Print Preview but text remains in colour?
PostScript to PDF Create Acrobat Layer
Transforming pictures from RGB to CMYK
Re: Issues with trapping a postscript file out of Indesign
Re: Problem printing PDFs from InDesign in OS X Preview
These and other discussions here. Most important: Postscript is old and outdated, it does not support transparency nor color management and if you have used EPS and ink manager it will be bypassed if a PDF via print is created.