Data retrieving for an PDF-based application form

Hi, Experts!

I'm new in the Print Workbench (CA-GTF-PWB) and I'm going to use a PDF-based application form (in tcode efrm).

I read that a layout in the Print Workbench is composed based on SAPscript or Smart or PDF-based form. And data are retrieved from a database thanks to Form class.

But PDF-based form has own interface that can be used for data retrieval.

And I have a question: which method of data retrieval is more useful, e.g. from the point of performance, for a PDF-based application form?

Thanks in advance,

Dmitriy.