Just note. If you have someone, not you wire up all your electronics and they are hooked thru the NEMA. If the main unit goes out, you are out there on the water without a depth finder or possible GPS. I've been in 2 boats where that happened. Main electronics went out. Fog rolled in. At least the compass worked and we knew how to use it. But when you are close to shore. You better know how to get back in without running ground. Dangerous situations. Don't want to be there again.
My personal reason for wiring every unit separately myself. I had 4 units, 2 console, one at the bow and one at the transom (used to fish tourney's). I've had 2 units fail at different times. They were 10 yr old units. I still had working units due to be wired separately.
Most do not use their compass (never learned) and would not have an idea how to get back without electronics.
If you wired it, you would have an idea where to look for the problem and might be able to repair out on the water.