[FISH11]

The DSI signal are supposed to be good to at least 200 feet (some models claim a little more), it is better for shallower waters. The screen looks almost 3D and Sonar (usually down to 1000 feet) gives you the different colors between soft and hard targets. Combined it allows you to see more detail that each one alone can't cover. The chirp technology on the Raymarine from what I have seen on advertisements and sales brochures just looks like the DSI image (it's provably just their name for their application of the same concept) That's just my opinion from what I have seen.