Update: Additional benchmarks comparing Tomcat configured with the APR connector vs. RestExpress 0.8.0 are published here.

Below are some charts comparing results of the four environments. The numbers were acquired by using HttPerf over various settings of the --rate= parameter, with settings ranging from 100 to 2,000.

Here's an example request with rate set to 375:
httperf --timeout=5 --client=0/1 --server=10.180.211.162 --port=8080 --uri=/?value=benchmarks --rate=375 --send-buffer=4096 --recv-buffer=16384 --num-conns=5000 --num-calls=10

The test configuration and sample source code can be found here.

The rate at which HTTP requests were issued to the server.

The average time it took to establish a TCP connection.

How long (in milliseconds) it took for the server to respond to the request.

The number of connections per second issued by the test (and conversely, handled by the server).

The average amount of network traffic (in kilobytes per second) during the test.