Balanced Routing distributes calls to all users without any priority. Each time a new call comes in the department, the call has an equal chance of getting forwarded to any of the available users. So, it is most likely that all users will receive an equal number of calls. Hence, balanced routing unlike serial routing ensures that all users get an equal load of calls.
Balanced routing should be used in the case where there is no hierarchy in the users and when all users added in the department should handle calls. You can take your sales or support department as an example.