Fabien Potencier just wrote an interesting post where he outlines what he believes to be the selling points of the Symfony project. First, let me point out that all of his points are 100% valid, and there's no doubt that Symfony is a great framework. I have great respect for Fabien and the Symfony project as a whole. That said, my concern with Fabien's post is that usually "selling points" for something imply that they are things that set something apart from the alternatives.
He goes through some of Fabien's points and makes his own counterpoints from the perspective of someone that's involved in the development of the Zend Framework. He notes that several of the points Fabien made are also valid about the ZF community and project as well - thriving community, a component-driven framework, code reuse, etc.
In closing, I'd like to re-iterate that Symfony 2 and Zend Framework 2 are both fantastic frameworks with a ton of brilliant people behind them. While Fabien makes some realistic points about things that make Symfony a great framework, he failed to point out that the same can be said about not only Zend Framework, but a handful of other high-quality PHP frameworks as well.