From my experience OpenPDF is better at formatting and layout. PDFBox is a lot lower level.

OpenPDF [1]:

  document.add(new Paragraph("Hello World"));

PDFBox [2]:

  contentStream.beginText();
  contentStream.setFont( font, 12 );
  contentStream.moveTextPositionByAmount( 100, 700 );
  contentStream.drawString( "Hello World" );
  contentStream.endText();

[1]: https://github.com/LibrePDF/OpenPDF/blob/master/pdf-toolbox/...

[2]: https://pdfbox.apache.org/1.8/cookbook/documentcreation.html