What you need to remember is that tools like "ab" and "siege" only give a static overview of the possible load.
The numbers you get from using them normally does not propagate to real world scenarios.
In your case I don't think this matters, since you just want to "showcase" results vs. other frameworks, so its purely statistic and not for instance configuration.
Though, for anyone that want to test their new application/website, I would highly recommend one of the services which offer real traffic during the test (most just spawn small instances and then use test cases to do specific things on your system). As this will give you much more valuable information on how much your system can handle at the current server/cluster configuration.