Reason most people are hesitant is these kind of questions normally start a usses versus themens kinda thing. They can normally get kinda heated. But you are correct that you need the extra $600 item if you go the Lowrance system.
Read all you can about each companies customer service record and make up your own mind.
I could tell you which one I prefer but only in a PM. Another great person to ask is Tom user ID Canepole. He is an electronics whiz and will give you the straightest scoop on them.
Garminarmin gpsmap 1040 xs networked with Garmin gpsmap 1242 xsv , Panoptix PS 30 and PS 31. Livescope LVS 32
Ice rig Echomap Ultra 106SV with LVS 12 and GT10-IF