RabbitMQ river performance question

Please advise!
I'm using RabbitMQ with elasticsearch server. I have an multithread application that's publishes messages to RabbitMQ. It wakes up one connection and for example three channels.

What's will be faster or better: publish one big message near 500-600 documents per thread, or publish 4-5 more smaller messages, near 100-150 documents per thread