Cheaper is for BaitI have had a great deal of success using an absolutely cheap knife as a bait knife and a quality knife as a filet knife. Actually, I use two knives for filleting fish. I have a custom made knife that holds an edge and has a strong blade. Harder to sharpen, that one is for heavier fish with thicker bones and tougher skin.
The other filet knife has a long thin blade and takes an edge very quickly. Unlike a lot of anglers, I use a sharpening steel instead of a sharpening stone when working through a pile of fish to clean. I will use the stone to put a good edge on the knife, but the sharpening steel is better while actually cleaning the fish.
Favorite StoneMy favorite stone is a bench stone that has both a course side and a fine side. Any nicks in the blade can be handled on the course side. The fine side helps me put a sharp edge down. Then the sharpening steel really puts a very sharp edge on the knife. I use a diamond embedded steel that really works well. The diamonds help insure that the knife blade is actually being cut and sharpened.
My MethodAs I clean one or two fish, I pick up the steel, hit the knife four or five times and go at it again. Just those four or five strokes really puts an edge back on the knife. The steel realigns the minute burrs on the knife edge making it sharp again.
My ChoiceI must say that the knife I use has a part in the sharpening effort. The Bass Pro Shops 9 inch filet knife is both inexpensive and it holds a good edge from the sharpening steel.
You can buy more expensive knives and sharpening products, and Im sure they will work well. But I do just fine with what I have. I sort of believe in sticking with what works, and this works for me.