Library vs. Controller

[eluser]xwero[/eluser]
I think you shouldn't see it as the advantages of a library over extending controllers. You have to decide if the code you are about to write is application specific or not. And if you think it's reusable you abstract it in order to make it as flexible as possible. If you find out that because of the abstractions you have to use too many methods or add too many layers, that is the sign the code is application specific.

But before you start extending the controllers see it hooks aren't possible. For a login and layout library this is certainly an option.