Most movies are shot in 2k-4k but there is no way the iPad's little gpu could play that. The main advantages are cleaner and easier to read fonts and photos. But at first glance, 150 ppi and 300 ppi look basically the same.
You at a certain point you cannot tell the difference between 150 dpi, 300 dpi, and 600 dpi depending on how far away you are. You don't want to spend 4x the gpu power on something that isn't going to look better.