I wanted a mega cab but dound a deal on the quad cab. The mega cabs are bad ass....having that much room in the rear seat area and still having a bed is sweet. My buddy has one and from the few times i have driven it, it doesn't feel any bigger than my quad cab from the drivers seat when it comes to maneuverability or vision.
One thing i will say is it seems like it is sprung lighter in the rear for whatever reason than othe configurations.
09 Dodge 2500 w/ a Cummins, dd/towrig
85 Toyota Pickup, 1tons, coilovers, 40's, ect