I think some if this comes down to what we are accustomed to. Physical books are what I am used to, having developed ways to flip quickly to find what I am looking for. It is easy out of habit, perhaps, just as typing on a keyboard is preferable to me over typing on a screen.
Perhaps, for those who have developed their own methods, pdf is easier.
That’s not to say I think one is better over the other. I think that if pdf publishers did things right, pdf would be a better option. Configuring pdfs to have tables of content and indices that link to relevant sections, references in rules to other rules that do the same linking, as well as a good old search and bookmarking that they already have could make pdf rules superior to even those with ingrained bias.
The first set of rules I bought in pdf for use on a tablet were cyberpunk and that was oh so appropriate.
I think GW embraces the capabilities if electronic rules, would be great to see others do even a basic bit of work to improve their usability for their customers other than “save as pdf” and done.