Minnowtime,
Both the 728 and 570 DI use the same display so the readouts between these two would be the same as far as the display goes. However, since the 570 DI use different sized 2D sonar beams and has the two additional DI beams; what you see on the display will differ from the 728’s due to the size and shape of the sonar beams. Using the DI sonar you will be more accurate in identifying whether it is structure and the type of structure you pass over.