It's very difficult to make any statements based on the data provided. Performance is obviously highly dependent on the system, the generator, the backend, the payload, request pattern, configuration, etc.
Over the past several months we have done quite a bit of performance tuning on Envoy and on very basic raw benchmarks it is inline with nginx (within about 10-15% for HTTP/1.1 -> HTTP/1.1, and equal or faster for HTTP/2 -> HTTP/1.1).
There are certain features enabled by default in Envoy that are expensive from a performance standpoint, such as request ID generation and dynamic stat generation. I have attached some configurations that we have been using to do the nginx comparisons. The Envoy configurations disable request ID generation as well as dynamic stat generation to make it more of an apples/apples comparison with nginx.
For load generation we have been using h2load from nhttp2 with a command line such as:
Thanks,
Matt