This is an impressively detailed benchmark, thank you for sharing your efforts.
However, was PHP's APC cache enabled?
Object-oriented PHP code should never be run without APC, the overhead of bytecode-compiling everything on every access gives a very slow and unrealistic picture of Symfony's best performance on web requests.
I am reminded of the Quercus "PHP compiler for Java" folks, who used to claim Quercus was hands down much faster than native PHP, until they finally tested PHP with APC. After that, their claim was only that the performance of Quercus was "comparable" to PHP with APC. It makes that much difference.
Thanks for clarifying. Object oriented PHP should never be deployed without APC. Shared hosting providers tend not to offer it, but virtual private server hosting (which can be very cheap, and is much more secure than shared hosting anyway) always does if it is being done competently for PHP. ServerGrove.com is a great example of the job done right (their VPS plans, not their shared hosting - they do that well but unfortunately APC just doesn't play well with shared hosting).