I have a Dragonfly fish finder. You couldn't pick out a fish to save your life on it, but it picks up the terrain of the bottom and structure really well. That is all I care about.
If you are looking for drop offs and such a down imaging works great. Here we have acres upon acres of flats and all of the fish are concentrated in tiny pockets. I could fan cast and get lucky or look for sunken tires from a marina or stumps ect and catch 95% more fish. coming into the time of year and going forward through March I will not take a sonar as the fish will be shallow.