I'd also rather have the books, as they are so much nicer to sit and read through, but they are dearer and if tea/beer gets tipped over them more hassle to replace. PDFs are great for gaming, as you can print out what you need and either laminate or reprint once ruined. For multi-player games with rookie players, you can print out multiple copies of what they need to play.
Also, the "Conklin’s Atlas of the Worlds" and such like are best in PDF, as you can print out as many maps as you need - especially if you have access to an A3 printer and can enlarge them. Also, If you have the facility to edit PDFs, you can produce your own playsheets, which are often missing from sets of rules

Like everything, each has it's place and uses and I'll continue to use both. Indeed for some favourite rules, I do have both versions - one to treasure and one to play with

.