The Nitrogen project web page declares equal support for yaws, mochiweb, and inets, but with which of these web servers is it going to perform the best? I.e. for a large scale application with mostly dynamic content with nitrogen + a web server which combination will be able to handle the most user load?
A question like this is highly dependent on the application. Any answer would have to be taken with a grain of salt and is definitely not a substitute for doing your own system tests. However, with all of that said, I believe the yaws and mochiweb are fairly similar in performance. yaws is the older project and may be more stable as a result but not neccessarily. I've almost no experience with inets so I'm not going to comment on it.
Your best bet is to run a set of benchmark tests for your app with each one and see what you get. It's so easy to switch between them in nitrogen that you can run tests with the same app and draw your own conclusions.