There are three main requirements which have to be kept in balance. These are urgency, importance and psychological readiness. Traditional time management systems have tended to concentrate on the first two of these. The neglect of psychological readiness is probably the reason that most people don’t find time management systems particularly effective or congenial. The most distinctive feature of FVP is the way that its algorithm is primarily based on psychological readiness - this then opens the way to keeping urgency and importance in the best achievable balance.
In GTD, at least how I understand it, prioritization is rational and conscious. In Autofocus / FVP, prioritization is based on your 'gut feeling' towards the task at the moment when you look at it. This was a crucial difference in my case.
(As for due dates, the author explicitly states that his systems are incapable of handling dateful tasks).