In general if I was using the mvc method, I would throw exceptions and catch them in a higher level in the application. If an exception is not caught then have the controller save it, so we can check for uncaught exceptions later and give our own error message to the user. It is also a good to store uncaught exceptions to a logger for analysis.

As for errors, I have a custom error handler which saves all errors to a buffer object until after execution of dispatch process has finished. The error system is too complicated for me to explain right now, but this way we can handle problems more efficiently.