Does the Pathfinder core rulebook contain any information that is not included already on www.d20pfsrd.com that would make it worth it to buy the PDF version of the manual? Or does it only have extra descriptive text?
Because of the nature of the rulebook, it includes things that are not part of the SRD. The website, while it contains a lot of the core rules, does not include all of the information that is laid out in the Core rulebook (Like the specific rules on how to make a character step-by-step, for example).
The d20pfsrd.com contains a vast wealth of information from the core books and is updated regularly, but I would not consider it a replacement for the core rules. It'd be like trying to play a FATE based game by just using the Spirit of The Century SRD.
Additionally, while d20pfsrd.com is very well maintained by a group of extremely dedicated volunteers, it occasionally has errors (which are typically corrected very quickly, but occur none-the-less).
Slightly off topic, but still relevant: By purchasing the Rulebook, you support Paizo, and thus make more core Pathfinder material possible.
I first purchased the Core Rule Book as a PDF just to get a feel for what I was getting myself into. It was worth every penny in my opinion. I however later purchased a dead tree copy for a few reasons.
- I like having the physical book on hand.
- Reading on a screen for long hours gets tiring and scrolling the PDF is slow.
- The artwork is amazing
When playing with a group, it's very helpful to have more than one copy of the books, and not everybody will have or want to use a digital device. Having at least one physical copy of the book is good, even if you do have various laptops and tablets around.
Also, Paizo have done really good work and are impressively open with the license, so it's good to reward them.
With multiple books, the srd search option can help immensely with tasks like finding and selecting spells. However, general comprehension of a class, specific monsters, and most importantly, combat rules, are all better tackled with the sourcebooks.
Knowing you are supporting paizo is also a huge plus.