- pre-conventional stage where right and wrong are determined based on whether something is praised or punished and where an action is chosen based on a cost/benefit, i.e. one is being pragmatic and rational---but life often doesn't encompass only materialistic behavior and both altruistic and manipulative behavior can have skewed scale due to people have different preferences/priorities;
- conventional stage where actions recognized as good by others are considered good, one follows the mainstream and could be hiding something while retaining the conformist image. This approach is fostering herd mentality, killing creativity and self confidence, and not giving much incentive for one to contemplate on his actions;
- post-conventional stage where actions based on one's own conscience are good, either he is enlightened or just playing god. Although such approach is needed when the current set of common morality norms/rules has yet to be specifically assigned to one's novel/unique conditions, often in such case asymmetric or lack of information persists and people just have different customs, values, cultures, habits, etc.
To the observation, these three are more of approaches rather than stages as they can happen simultaneously, i.e. conventional approach provides the general evaluation for pre-conventional approach. Although for most of the time they do agree with one another, exceptions do happen--in which we need to tread things more carefully and taking multiple/deeper perspective.
Well, at the end of the day: model is just a model. You chose what fits you best, but you still need to be open for other options (and updates).