The Play example was totally unfair since it blocks on the database query which will block the underlying event loop and really lower the overall throughput.
The problem is that the database queries were done in a blocking fashion. The test essentially blocks the main event loop which is of course going to kill performance.
The play test was written totally incorrectly since it used blocking database calls. Since play is really just a layer on top of Netty it should perform nearly as well if correctly written.