There's actually no reason to choose Pulsar anymore. Pulsar has even more layers with Zookeeper + Bookkeeper that requires something like Kubernetes to run well. It was great 5 years ago for heavy users who need better scalability and features than Kafka, however the development has become a mess.

With the removal of zookeeper and tiered storage (separated from compute), Kafka has caught up on scalability while being simpler to deploy. It also has a far bigger ecosystem with more polished features like ksqldb.