Both nginx and apache are powerful and effective servers - we are using them both!
Apache currently reigns as the #1 server for websites and since its public release in 2006, nginx has taken the world by storm and is now the #2 server for active sites. The reasons for each respective server's popularity are clear: apache's power and nginx's speed are well known. However, both servers do have drawbacks—apache is hard on server memory, while nginx (great at static files) needs the help of php-fpm or similar modules for dynamic content.
However, one can combine the two web servers to great effect, with nginx as static web server front and apache processing the back end - that's what we did!