I tend to prefer SF that is not either. After all most of the time most of the world is neither so why would the future be any different? Still this was important to early SF & some of my favorite works deal with the theme. For example much of Cordwainer Smith's work deals with humanist utopias, usually in a hostile way.

Yet on the whole I think dystopias tend to be more memorable. This may be because there is more dramatic potential there. Well regarded dystopias include 1984 by Orwell, Brave New World by Huxley, & We by Zamiatin. Never read any of them I will admit. Still when they are as old as proposed Utopias like Looking Backward by Bellamy or News from Nowhere by Morris I feel they will probably be more popular than that book is now.