I have the basic understanding that ね is generally more formal/feminine and な is generally more informal/masculine. I was told that you tend to use ね as an emphasis if you are a) a female yourself or ...
OK, really esoteric question time: So I went to the cinema with a female friend on the weekend. I was going to buy some of the horrendously overpriced popcorn there, but then she said: 持ってきちゃった! ...