The pros and cons of categorizing children into three general types of temperament both have to do with the fact that there can be a great deal of variation within each temperament. That is, not all children who are categorized as easy (for example) are identical to one another. This brings about both pros and cons.
The major pro is the fact that categorizing children makes it easier for us to understand them to some degree. As mentioned above, there is a great deal of variation within each temperament and each child is different. Categorizing children allows us to have some hope of understanding them better without having to study every aspect of their personality. We can simply look at a child and say that they are easy or slow to warm up instead of having to try to understand every facet of their personality. Categorization, then, saves us the time and trouble of having to study each child in great detail.
But this is also the problem with categorizing children. When we categorize them, we overlook the differences between them. If we have, for example, three children that are all generally categorized as “easy,” we might treat them all in the same way. This may be less than ideal because the children may be different in important ways. By categorizing them, we gloss over these differences. When this happens, we do not treat the children in the optimal way.
With regard to individualist and collectivist societies, it is hard to be objective since we (I am American) are members of what is often said to be the most individualistic society on earth. Therefore, individualism seems “normal” to most Americans and collectivism will often seem to be disadvantageous.
I would say that individualism is good because it teaches children to be independent and self-reliant. This allows them to take care of themselves in a variety of situations. On the other hand, individualism can make children more self-centered than they otherwise would be. It can teach them not to care as much about others as would be ideal. I would say that collectivism has the opposite advantages and disadvantages. It encourages children to care about others, but it can also make them less able to do things for themselves.