I have the hummingbird 797 si with side imaging. The side imaging gives detailed, almost 3d picture of structure. Passing a bridge pilon is pretty cool as you can see it in detail all the way to the bottom. In Frankfort there is an old covered bridge that sits on the bottom of the KY under the "singing bridge" that replaced it. You can see it plainly (although it is now collapsed). Our county search and rescue has very high end side imaging sonar and I will not go into what they use it for. If you want a unit that will give very detailed structure such as underwater cliffs, downed timber, or a sunken barge side imaging is the way to go. The other benifit to side imaging is my 797 si gives you a view up to 150ft left, 150ft right and a view directly under the boat. So you see a much larger picture than with the single view bottom units of about 40ft. You can ^ sensitivity to as close as 40ft side to see bait fish and fish. The only distortion I get is when making sharp turns as the side view gets streched or compressed depending on the side. Have not used the Lowrance model, however, they do make quality products. I would recomend side imaging!