How is it that some vamps turn out with a conscience and others are rogue?

I think it has a lot to do with the kind of person you were before they were changed and Vampires have a minnd of there own so they choose to be the way they want to be. Only your body dies when you are changed into a vampire not your mind...over centuries your your memories will fade but if you live a certain way for a long time(Example:with a conscience, the moral way) you will continue to do so.