I prefer male writers, largely because most of the female-written books I know are chick lit, which I absolutely can't stand. It seems to me that women write to make a point, whereas men write for more intellectual reasons. Women are more idealistic, and consequently, their books are likely to reflect that. Men are more realistic, even pessimistic, and I think that can be seen in many male-written books. Women are often more subjective than men.
That's not a bad thing -- it's just that the kind of books I personally like to read have a slightly more intellectual and less observational bent. If I liked chick lit I'd almost certainly prefer female writers, because they're better at the real human stuff (again, IMO).
Of course, there are exceptions. The Harry Potter books, to use one example, are written in an almost masculine way (IMO). I can't think of any male-written books that sound feminine, off the top of my head.... There must be some, though. Hmmm.
EDIT: Thought of one. Tess of the d'Urbervilles by Thomas Hardy. That's written by a man about a young woman, and it's so sympathetic to her (especially striking given the time it was written) that you might think it was a woman if you didn't know otherwise.
Jas