as reedo said... there is no correct answer. it is down to your opinion of what you personally like more. it is done to create more contrast or deeper blacks but has certain downfalls as well.
mine is not edge lit (i have an older ccfl backlit model) but is a sony with non-local auto-dimming and i finally got fed up with it. the tv constantly adjusts the backlight and goes light-dark-light-dark which is very annoying. i finally just set it to game mode so it stays at a constant setting. while i might lose out on deep blacks for some scenes this is preferrable to me as the flickering from scene to scene just got on my last nerve. my opinion of course.
now, on grid-array backlit tvs zone backlighting/auto-backlighting certainly makes alot of sense. on some multi-edge lit tvs its not terrible as well.