The more waypoints and routes a unti can hold the better it is. Some units will connect with a personal computer to upload or download this information. If you are covering many different areas, this may be an important feature. It should have adjustable contrast for use in different lighting conditions and a backlight for night work. You should be able to turn the night light off easily to save battery power.
Some units turn off automatically after a pre-set period of time with no inputs.
This is a good feature to furthersave batteries. As further protection for internal electronics, they are filled at the factory with dry nitrogen gas to keep moisture out. Map chips are currently available for the Great screen with the current position accurately overlaid on the map. Map chips are currently available for the Great Lakes and the US East Coast which more regions being added quickly. Few electronic land maps are available at this time.