Not all displays are designed for the same applications. Here's a quick explanation of some of the different TFT (thin-film-transistor) displays you may come across and which situations they're best suited for.
TFT TN (twisted nematic) displays utilize backlight, polarizing glass, and electrode layers. When voltage is applied, it twists the electrode layer, which turns pixels on and off. While this is a versatile display, it has limitations when it comes to color reproductions and viewing angles. For example, it would not do well outdoors and must be viewed straight-on for best results:
On the other hand, MVA (multi-domain vertical alignment) displays differ in their polarizing glass layer. The glass layer for MVA displays has ridges in it to create randomization in the crystal alignment. When voltage is applied to this display, the randomized crystal alignment throws light in many different directions, which improves viewing angles:
If you need your display to be readable in direct sunlight, however, you'll need to find a display that offers more brightness. Part of display brightness obviously comes from the brightness of the backlight layer. However, light can also be maximized with the use of BEF (Brightness Enhancement Film). BEF refracts light emitted outside the conical viewing angle back through the backlight until it can exit directed towards the viewer. This allows up to 60% more brightness (or more if a second sheet is crossed at a 90° angle).
Size and Cost
Off-the-shelf displays are preferable to custom displays when it comes to costs. This is why so many manufacturers choose to produce their displays in multiple sizes in addition to multiple performance types—they aim to suit the needs of many different applications so designers won't need to order custom displays.
The displays used in this video are all 800x480 transmissive-type TFTs with capacitive touch capabilities and I2C interface. There are, however, myriad displays available and this information should prove helpful for choosing between them.