Apache Kafka is a robust, reliable choice for high-throughput systems, especially in organizations with existing Kafka infrastructure or expertise. For instance, in a scenario where a company has multiple services that already use Kafka for event streaming, and they need to maintain compatibility and ease of integration, they would choose Kafka over Pulsar.
Apache Pulsar is often preferred when a project requires multi-tenancy and geo-replication out of the box. It's also suitable for applications that need a more flexible messaging model with different subscription types. For example, in a global application needing real-time analytics from different geographical regions, Pulsar's geo-replication can efficiently manage and replicate data across those regions without complex configurations.