I think the most clear down imaging is from transducers that
have dedicated crystals for that.
Otherwise, the sofware will just combine the two side-images into
a down image.
Down imaging is as it states, looking straight down.
It's just a different look than regular 2-d sonar.
In my opinon, down-imaging is way overrated.
I could never make out anything on my 1197c.
It wasn't very clear looking.
I dont' even use it anymore, and have hidden the down-imaging views.
I prefer 2-d conventional sonar for on the water.
And side-imaging for recording and reviewing at home.
I think you can't go wrong by getting the best side-imaging
unit you can.
If it also has dedicated crystals for down-imaging, then so much
the better.