As a long time kayak angler and kayak fishing shop owner I'll add this:
Humminbirds are allergic to saltwater.
Personally I have 4 Hbird units in a box in my garage. Hbird wanted $60 to diagnose the problems on each and it wasn't worth the money to me. I'm now using Eagle units. My Pro Angler has the Eagle 350 GPS/Sonar combo and my Revo has the Cuda 168. They just discontinued the 168 and the unit we're using in the shops is called the Cuda 300 (it's the old 242 with a new paintjob).
The OEX shops all use Eagle exclusively because of their durability in the saltwater. Eagle is the "value" line produced by Lowrance. I took the Lowrance sonar education seminar where we used their high-end color/gps/sonar units and it was fun but personal conclusion was that color was over-rated for kayak use as we are moving so slowly and shooting through-hull. The units I use are powerful enough to give me bottom composition detail (mud vs sand vs weeds) and I can tell the difference between kelp, floating debris and fish so what more do I need?
The last piece of my decision making tree is price. If I lose a $300+ piece of equipment that hurts. The Cuda 300 is only about $120...