picture quality: PLASMA is it
the problem with plasma is the plasma gas between the panel is unstable when subjected to sudden temperature changes.
got 2 42" philips plasma (one was replacement) all suffered with the same problem - distorted screen. now i switch to LCD.
if you used to watch plasma, one major thing you'll notice is the screen reaction time where you'll notice a certain lag with the movement in the screen specially when watching sports.
as advised, when buying LCD, check the reaction time. it should not be more than 8 milli seconds. mine is 5ms, brand SAMSUNG