What's Better, NIO or IO? On Benchmarking your Server...
By pelegri on Apr 03, 2008
Scott compares simple and complex cases: in a simple request/response case the overhead of the select() call implied by NIO is noticeable, but in the more complex case where you need to scale, NIO is the clear winner.
Check out Scott's note and you may also enjoy browsing other entries in his blog.