Pulsar is better for very large scale deployments provided you have people to manage it
The only thing I can see that can make this true is Pulsar seems to have better elastic scalability. But it seems to score less on everything else. It has a much more complex storage system that ends up not matching Kafka's high-end throughput at large scale.
From what I recall, Twitter ended up abandoning BookKeeper due to storage scale concerns. Related: https://blog.twitter.com/engineering/en_us/topics/insights/2...
Pulsar likely would have been considered if it was more mature at the time and sported a community of comparable size to Kafka (it's still a long way from this).