Interesting question!
As a reader, I prefer longer chapters, ideally posted ED or EOD, since the shorter the chapter and the longer the time between chapter posts, the more likely it is that I will forget some important facts about the story to-date. (Ever since my son was born, I've had a mind like a steel sieve.)
As a writer, I try not to post parts shorter than 10 pages or so. My first multipart post had started with much shorter parts and, based upon reader FDK, I wound up making subsequent posts much longer.
But I second Anti-K -- quality is, of course, more important than quantity.
Joy,
Lynn
