The best answer might be both.
In the past I liked to print and read, but with larger higher resolution monitors now, I'm finding myself reading more and more online from the browser. Still often I like to print pdf of some content so I can leave it on my desks for later review, read it at the dinner table
, etc. PDFs allow easy printing exactly the way you format it which is good. But HTML + CSS allows you to do better directly in the browser since you don't have the delay of the adobe reader involved which sometimes stalls browsers a bit for me.
(I've not been very impressed to date with database to both html and pdf in one step (e.g. the print this page pdf icon in many cms packages) as usually that results in a half-baked pdf that's not really formatted that nicely in the scope of pdfs.)