To me a great piece is a sequence of memorable sentences. And I know that’s a sort of limiting thing. Maybe that’s why I can’t write effective narratives! But for me a wonderful epigrammatic sentence, an effective aphorism, that for me is like seeing a pregnant woman, it’s the perfectly shaped thing, pregnant sentences.
And then paragraph structure fascinates me, too. One of the things that drives me nuts when I’m reading even good academic writing is that nobody seems to have ever heard that sentence variation is a vital part of writing. These are people who are perfectly competent in every other ways, but every sentence is the same shape.
In the end though, you either can produce surprising, beautiful sentences or you can’t. Without that, all the erudition and intelligence in the world is not going to make any difference. For me, yes, a piece works when I can say that there are six good sentences in it. And a piece that does not have any good sentence is not worth reading. Now, having said that, of course I struggle over weeks and pull my hair to work on the structure, to make it logical, and move paragraphs around so that the sequence flows. All that stuff matters, too. But if I am answering honestly, yes, it’s the sentence that matters.