Out of curiosity, are you using the durable, NATS-Streaming server, or just the ephemeral NATS-server? I’d be interested to hear more about the performance differences you see.
The real allure was the guarantee that only one subscriber would get a request much like a traditional load balancer. The performance was an added benefit.
When we put it together a few years ago the cloistering wasn't very mature and the streaming version with persistence wasn't completed. Would look into this over kafka if only for the simplicity in management and track record of go for performance and reliability.