The 571 is a stand alone unit and cannot be linked or Ethernet-ed to any other unit ...

The 798 and 571 have been very reliable units for several users thru the years ...

The 798 has 2d, blended DI from SI, SI, and GPS ...

The 571 DI has 2d, and dedicated DI ...

The dedicated DI from the 571 will give you good comparison to the things you see on the 2d images ...

The SI from the 798 will help you find things in your waters that you never knew where there ...

Rickie