These things are important for communicating with parents because they allow parents to get regular updates about what is happening in their child’s classroom. The two devices have somewhat different uses.
Newsletters are better for giving parents general information about what is going on in their child’s room. The newsletters do not really tell the parents much about their specific child, but they do give regular opportunities for parents to know what sorts of activities have been going on in class.
By contrast, journals can be very good for letting parents know what their specific children have been doing. If the child writes in their journal every day, the parents can learn about what the child is thinking about at school. They can see evidence of the changes that are going on in their child’s writing ability. This gives them a view of what is happening at school that is much more focused on their own child.