My first requirement is to have high end lake maps so that I can navigate, find and target areas that I suspect are holding fish. Once I am in that area I will use DI or SI to locate any fish that are there.
Out in the open lake I like a fast reading good sonar to show where fish and bait are suspended. Here is a good place to use DI or SI to see if the return is really fish and what kind they might be.
On the screen display I want water temp and depth and boat speed.
With all the features of today's fishfinders it's hard to keep it simple but the less I have to look at the easier it becomes to use. I never use split screen but if I had one of those units the size of a TV set I might
FWIW, I am about to list a Lowrance LMS-344C IGPS for sale in the classifids as soon as I can get some pictures taken. This is a pretty good little unit for it's size and would be great for a bow unit or entry level fishfinder with lots of features.