I personally prefer the PDF files. If I want, I can print out loose-leaf, and put them in a binder or comb-type book.
But mostly, I can print out as many copies of a page as needed, for future children or if we need to re-do a page.
I also like things instantly. I can save a PDF to my Google documents, and then access them wherever I am, whether that be on vacation or simply on a different computer.