American Angler makes a really good 120 volt knife. I have not tried there 12 volt one. I'm going on my 6th year on mine. Used to go through one every year or so. The trigger would go out on them. I used to clean all the fish on the boat while we trolled. Found that the knife would not cycle fast enough to suit me if the battery wore down a little, with the motor running you were basically running off of the alternator which would cycle the knife faster. Key to doing a good job quickly with an electric knife is sharp blades, a knife that cycles quickly, and learning how to keep your angles to maximize your fillet size - not waste meat, while finishing them in a timely manner. I have never been able to resharpen the electric knife blades effectively - just buy new ones. I prefer the blades with the less aggressive teeth, waste to much meat with the really aggressive ones although they will cut through the rib bones more quickly.
Watched Tim Bagley's video on filleting stripers about 6 years ago. Ordered a 9" Dexter Russell knife that evening. My son got me a 9" Bubba blade for Christmas last year. Use the Bubba Blade to cut off the fillets and the Dexter Russell to take the skin and 90% of the red meat off with the skin. Using this process I am 3 times faster than using an electric knife on stripers. Use my American angler 120 volt on all other fish.