Is there a difference, small or significant, in how the two models handle or dissipate heat? In other words, just cause the 27 inch is larger, presumably, there's more room/space inside? Does this allow more air flow, better venting, as oppose to the smaller 21 inch? Using this line of thought, the 21 would therefore be more crammed together and have less airflow? Or is there like zero difference? I ask because I was using a 27 inch at work today for a special job, and running videos on it all day, basically, and it felt like the back never got very hot.