Any claims about "fastest webserver" also need to add the qualifier "free". Because I believe litespeed is faster, though the free version has a simultaneous connection limit. It's even faster than nginx in some cases. http://blog.litespeedtech.com/2010/01/06/benchmark-compariso... Also, litespeed is practically a drop-in replacement for apache since it can obey httpd.conf and .htaccess files which no other webserver…
For Rails work these days though, I'm using passenger with either nginx or apache.