Japanese Knives and Western Knives may appear similar at first glance, but to a professional they have one small change which make a large difference in how they prepare food. Japanese knives have a beveled edge on just one side, the other side of the blade remains flat. On a Western knife the cutting edge is typically beveled on both sides. Japanese knives are designed in such a way that perfect 90 degree angles for sashimi are achievable, with any Western design knife the resulting sashimi would have a scalloped edge.
The only downside to this design is that Japanese knives are specifically left or right handed, while a Western knife can be used with either hand. The Kataba is used for filleting whole fish and for achieving straight flat cuts. Western knives leave rough edges, which hinder the absorption of flavors during cooking. Western knives are more practical on tough foods, like beef, especially to get them down to manageable size. The final cuts however are often best made with a Kataba which allows for speed and control.
Western knives are made with a softer steel than Japanese counterparts. This results in Western knives being much thicker. Western knives are often sharpened to a 20 degree angle on both sides, resulting in a 40 degree profile. A Usuba, is cut to a 10 degree angle on one side and flat on the other, making the total profile a mere 10 degrees. If you were to sharpen a Western knife in a similar ,10 degree profile, manner it would crumble like a piece of tin foil as soon as you cut anything with it. A Usuba can be chipped easily, but the whole knife is much stronger than a comparable Western knife.
Japanese knives often maintain their sharp edge much longer than Western knives. This is due mainly to how they are used Western knives are banged down, while Japanese knives are dragged across, this results in the blade being protected from force which damages it more quickly. Honyaki-Bocho knives are created from a solid piece of raw steal that is forged and tempered. The blade of a Honyaki-Bocho is easier to sharpen, but the Kasumi-Bocho is considered superior by many chefs. Kasumi-Bocho take longer to make as well as sharpen. They require more work to sharpen and maintain, but maintain their cutting edge much longer and have a longer life in general than the easier to sharpen Honyaki-Bocho.