Screen angle and brightness
This is affected by the manufacturer of your device, as well as your own device settings. Different manufacturers use different types of screens for different devices. Some of the different types are: TFT-LCD screens, as well as different kinds of AMOLEDs. I have had one Sony and one Samsung, and have noticed that even though the Sony has higher pixel density and brightness, it cannot be viewed from certain tilts and when natural sun light reflects on the screen, its content goes practically invisible until shaded.