This is one of the smallest Humminbird units with SI and DI technology on it, and also one of the cheapest fish finders available featuring these options. Similar to the other Humminbird fish finders within the 300 series, the Humminbird 398ci SI Combo is equipped with a small screen 3.5-inch in diagonal, 320×240 pixel resolution, LED backlight, full color.
The Humminbird 581i HD DI Combo, is also one of the new models with HD display and Down Imaging, as it’s name suggests it. Although it only features a black and white screen, 16 lvl grayscale, the images for both SwitchFire and Down Imaging, and also the mapping displays, are quite clear and accurate.
The 581i HD DI Combo has a medium size screen, 5-inch diagonal, 640×320 pixel resolution. Along with the Down Imaging option, come quite a few other very useful features. For example, this