Both of my kids read both, but with a preference for fiction--stronger in my DD. However, she has read every nonfiction book of interest (and some NOT of interest) in the children's area of the library about birds, and many in the adult section. Nobody here reads biography.
I personally notice a lot of poor-quality kids' nonfiction--ugh. Maybe my library is not good at this? I think my kids would read more if it they could find more they liked. They were both totally crazy for Magic Schoolbus (not exactly NF, but close) and read every book in the series, chapter and picture.
I do find a bit harder to find books for DS6 than I did for DD at this age. Well, I take that back. I find it harder to find GOOD books for him. I feel there's plenty of book "boy" series dreck, but more girl-oriented lovely classics.
