The 5.7″ QVGA (320×240) is an older standard than the 4.3″ display, and that’s why the 5.7″ has lower resolution. In general, the lower the resolution, the higher the brightness, so the 5.7″ does have one redeeming feature. We favor “standard” sizes and resolutions as much as possible for long life availability. There are no standard bodies for small TFT displays, only form factors and resolutions that get adopted by multiple vendors.
You have several options for higher resolution. These are all powered by our SLCD5 controller. All of these options are very similar in resolution (dots per inch (dpi) or pixel pitch).
Reference 4.3″ dot pitch 0.198mm = 128dpi
All of the above are available from multiple panel vendors.