"Berate" is more emotional and angry—it is used to show that the person is yelling or being very hard on the person who made the mistake. "Reprimand" is more official, and may not be emotional at all. So, for example, an employee who comes to work late will be reprimanded, not berated (at least, not in a professional company!). However, a frustrated parent may berate a child for spilling milk on the sofa.