I always look at number of engines vs number of seats and how likely am I to survive an emergency evacuation (down the slides) taking in to consideration parents grabbing toddlers, idiots going for their hand baggage and duty frees in overhead bins and just the general panic of an emergency situation.
According one shall not find me flying in an A380 anytime soon, B777-200 is acceptable, B777-300 is questionable but give me a short A340 anytime you like
