As far as sun/moon goes, there's a few pieces to it. Not only are those two signs important, but its important how those two signs 'feel' about each other.
For example, I know several people that have a sun/moon combination with signs that don't 'get along'. I find this makes a person fickle, and often contributes to unhappiness, as they often feel pulled in different directions, or they make choices they always seem to regret. It isn't simply that the person has the influence of both those signs.
Another thing is, its not nature vs. nurture. Its nature and nurture. There are some events that may be traumatic to a Cancer that a Scorpio may not be all that bothered by. So not only are you contending with the zodiac energies, you're adding life experiences to be combined to the already present astrological influences.
I'm certainly not an expert(at all), but these are just some conclusions I've come to through the years.
