Compare nginx+Apache+mod_wsgi vs nginx+uWSGI?
When you load your typical large Python web application on top of the most popular WSGI servers, the performance difference isn't actually that much and usually nothing to get excited about. Hello world benchmarks like the one you quote are very misleading as they test a very narrow use case and the configurations used are usually never comparable. You should consider watching my PyCon talk which talk about bottlenecks in web servers and web applications.
http://pyvideo.org/video/703/web-server-bottlenecks-and-performance-tuning
Given that the WSGI server is not usually the problem, you should just choose that which you find easiest to manage and has the sorts of features you think you will require. Then use benchmarking and monitoring of that choice to work out how to set it up so as to perform best for your specific web application. Even then, any increase in performance or gains in user satisfaction are not usually going to come from such tuning.