Santoku and Nakiri knives are similar in that they share a Japanese heritage where both of these knife styles originated.
A santoku knife is a general purpose knife that excels at slicing, dicing and mincing. The blade of a santoku knife is typically between 5 and 8 inches long with a flat edge and a “sheep’s foot” blade that curves in an angle approaching 60 degrees at the point. A sheep’s foot design draws the spine of the blade down to the front with little clearance above the horizontal cutting plane while the blade is naturally resting from heel to forward cutting edge. The top of the santoku handle is in line with the top of the blade, and the blade and handle are designed to work in harmony by matching the blade's width and weight to the weight of the blade’s tang and handle. The original Japanese santoku is considered to be a well-balanced knife.
The sheep’s foot design of the santoku knife provides a linear cutting edge with limited “rocking” abilities like those found in a Chef’s knife. The santoku design is also thinner, lighter, shorter and more hardened than the traditional Western chef’s knife. The standard Chef’s knife is typically 8 inches, while a santoku knife is generally 6 or 7 inches. The blade of a santoku knife is harder than a Chef’s knife and for the average user they are harder to sharpen, though if used as designed the santoku will hold its edge longer and require less sharpening. Though there are exceptions, santoku knives do not typically have a bolster, though they often have “scalloped” sides (known as a Granton edge) and maintain a more uniform thickness from spine to blade.
A nakiri knife is designed for cutting vegetables. Nakiri knives allow for thinner cuts of vegetables than a paring knife as they have a straight blade edge for cutting all the way to the cutting board without needing horizontal pull or push. Nakiri knives are also very thin so as not to break vegetable slices. They are for use in home kitchens primarily and generally have a black blade.