I can't stress this enough. Besides all the configuration settings, you can really dig into the internals.
Our production deployment of Apache is custom-compiled with something like 90% of the modules disabled. Only the basic stuff we use.
Each deployment is unique, making benchmarks pretty useless.
If you need to choose which httpd to use, decide based on how easily it'll fit in your stack. I promise you, if you hit the performance ceiling on any of the httpd suites out there, you'll have bigger fish to fry.