I am trying to take the mystery (to me) out of why QT4 is better than qt3.

I spent hours porting an application to QT4 but i'm still a bit ignorant as to why i did it.

I would like to write something about the powers of QT4 in the report on my project.

So could someone tell me, or direct me to articles that clearly list and explain why qt4 is better

example:

Does the qt4 API give better performance in terms of speed,and how does one take advantage of that?

what exactly does this statement on the model/view architecture mean? and why is it such an improvement? (from qt assistant: What's new in QT 4)

Since the model takes responsibility for supplying items of data, and the view takes care of their presentation to the user, we do not require item classes to represent individual items. Delegates handle the painting and editing of data obtained from the model.
How exactly does

a modern action-based mainwindow, toolbar, menu, and docking architecture.
provide

a more consistent and efficient framework for main window management.
what were the problems with how the mainwindow code was written in qt3?

Is the new API faster in anyway?

If so, in what way, what aspects of it makes it faster?

Please feel free to be as generous as possible with your response.

Thanks in advance for your attention and time.