The framework is one thing, how you use it is more important and I believe once you know any framework ( and in any language) inside out, it's kinda pointless to compare. Anything will do, unless you are writing a new super duper cool Google, Twitter of Fb

Also strange, after reading 51 comments, i have not seen anyone mention Zend Framework. It's got a steep learning curve, but it's just awesome. I've been writing a social web app framework based on ZF, Redis, Gearman and lots of other stack and it's awesome.