One error many cutlery enthusiasts make in discussing knife quality is overemphasizing the blade's hardness. Perhaps it is reducing decisions to simple comparisons of numbers.

Hardness can be measured by the Rockwell hardness test using a piece of industrial equipment that looks like a drill press. A diamond-tipped instrument is lowered onto samples of the materials being tested under uniform pressure and the results read from a dial. The less penetration, the harder the steel. But if you conclude the harder the steel, the better the quality, you are wrong.
Two different steels with identical hardness ratings can have different edge holding properties (wear resistance) because they are composed of different alloys. And knives are used for cutting, not for deflecting diamonds. Besides, a knife may need to be flexible or rigid (tough) or not rust (corrosion resistant) based on its application.

To make matters more confusing, two factories can order the same steel from the same supplier and turn out products with different characteristics. This is because no two shipments of steel come from the mill with exactly the same chemical properties. And the quality of the tempering and finishing process, as well as the design of the product, can affect the performance of the blade.
For example, polishing a blade, blasting its surface with glass pellets, or other techniques can improve corrosion resistance by encouraging moisture to bead and roll off.

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