I have had both. A 797c2 with external and now a 798ci which is internal. I use my unit in multiple boats, including a portable set-up. Always needing the external receiver was a pain. The units with internal (at least the 700 series) will automaticly switch to external if the receiver is present. So, when I upgraded, selected the internal receiver. On my main fishing boat, I have the now discontinued High Accuracy external receiver, and that is mounted near the SI transducer. You can get the 798ci, and when needed add an external, if you need additional accuracy or problem with internal receiver sat reception.