Dedicated DI will always be better than DI from SI ...

The Main Axis (strongest part of the sound pulse) of the thin slice DI beam is pointing straight down ...giving strong return echoes from stuff directly under the boat ...

The Main Axis of the thin slice SI beams are pointing 60° to each side - leaving only weaker echo returns from stuff directly under the boat = to be rendered into the "DI from SI" computer generated DI image ...

Rickie