I have posted the following answer for another question, though it may be more appropriate here.
MVC is good for plain server side scripting. In MVC developers always try to keep the controller very lean. Mainly controller is for just selecting the appropriate model and reflect on the view. But in today's web applications the View part has radically changed and became complex enough to produce a big, fat and messy controller. So now we need a new place to put the user interface's complex control logic. Here the P of MVP comes in that is the presenter. So presenters are responsible for controlling the logic for a particular user interface component. Don't worry the controller is still here, named as Application Controller. Which ultimately responsible for switching between comparatively larger application components. So MVP can also be said MVPC(!!). BTW this was my way of understanding MVP and obviously not any ground rule.
So I am already tend to MVP for complex web apps.