nginx won over the apache threading model and here are some benchmarks
and papers about the model

http://scoop.simplyexcited.co.uk/2010/07/05/node-js-brief-overview-2/

http://stackoverflow.com/questions/2583350/is-epoll-the-essential-reason-that-tornadowebor-nginx-is-so-fast

http://www.slideshare.net/marcusf/nonblocking-io-event-loops-and-nodejs