Tobias Schlitt has, for a personal project, put together a comparison of caching with two different web servers he's building applications with - Apache and Lighttpd.
For a little private project, which makes extensive use of caching, I recently checked, where I could get gather some more performance from.
He had been pointed towards Lighttpd by Kore (who recommended it based on his experience with it). So, Tobias tested the application on both of the two servers with somewhat predictable results (see image). Apache was slower in most cases and quite a bit slower when it came to working with larger files.