A large number of pilots think the only way to have a good readability is to increase the nits (~ brightness) or to use a eInk screen (black and white). The most important factor is the angle of the screen with the look (perpendicular) and not the nits/brightness).
Read more details about best brightness setting in this FAQ.
Read more details about link between brightness, readability and autonomy in this FAQ.
In the “Readability matters” page, you can see a comparison between AIR³ 7.1 and AIR³ 7.2 (1000 nits). Tilting the screen is the most efficient way to increase readability.