> In we know that HTML is going to be much more compact (and compressible!) than PDF and that's the biggest advantage I see on a web where bandwidth still matters.

PDFs can be tiny if they do not embed fonts. Serving fonts is very much a complex technology in HTML world.

Browsing the web is a pain in the ass if you don't use a browser compliant with up-to-date standards, but the whole "HTML can be lightweight" argument pretty much depends on avoiding much of today's standardisation. As an objection to the original argument, it is not comparing like with like.