In BigQuery Client, you do things by yourself, more of a hands on approach. In Apache Beam it is like you have a robot assistant that can do most of the things for you.

You have to handle files and format by yourself in BigQuery Client, but in Apache Beam it automatically writes files and does breaks if needed.

BigQuery Client is ideal for simple loading while Apache Beam is well suited for large scale data processing, as Apache Beam starts and runs the whole process. BigQuery Client starts with your script or command.

BigQuery Client and Apache Beam loads are not really the same but it does the same thing, to load data to BigQuery.