There's a problem too with long-winded SF authors: they leave too little to the imagination. Most of my fave authors write fairly succintly, with gaps for my imagination to fill. This makes their stories seem more real and exciting.

I would say "some" rather than most, and the best are not deliberately obscure: look at writers like Fitzgerald, Bellow, (some) Updike, Flaubert, Hemingway and

Others are more difficult to read because of the nature of how they try to express reality, feeling, and point of view, like Virginia Woolf, Joyce, or Proust.

But I don't think neither is all that obscure or all that direct, as both words seem to be synonyms for the same ideas expressed along the axis of "nature" and "artifice" that James Wood describes in _How Fiction Works_.