In this new post to his blog Marius Stanciu-Sergiu suggests that if your question is "what framework should I use?" you're already headed in the wrong direction.

You're already off on the wrong foot. The reason? You're thinking you need a framework to get whatever you need done. All too often I see posts on forums: "What framework should I use for a large networking site, like MySpace?" If you have to ask, you're doing it wrong.

He suggests a few other questions you might ask instead - how to gauge framework performance, does it support memcache, what kind of templating does it allow, etc. There's no simple answer to the question of which is best for you and your project and there's certainly not a one-size-fits-all framework out there.