We often discuss XML and JSON as the data formats for client server computing over the web. Another format – Protocol Buffer (protobuf) – is gaining ground. It is a binary format and the size of messages are much smaller than XML or JSON.
But, things begin to get cloudy. XML and JSON can be compressed in flight. Compressed XML and JSON messages are actually smaller than protobuf.
Even with compressed XML and JSON, benchmarks show that protobuf can be faster. This IBM DeveloperWorks article gets into that. Note: The article does not explicitly say that the performance benchmark was done for compressed XML and JSON. The author has confirmed that in the follow on discussion, seen below the article.