Although carbon steel blades take a better edge than either regular or high carbon stainless steel, they tend to lose their sharpness quickly. Also carbon steel blades will discolor when they come into contact with acidic foods. The metal is brittle and can break easily under stress.
Stainless steel is much stronger than carbon steel and will not discolor or rust. It is difficult to get a good edge on a stainless steel blade, although once an edge is established, it tends to last longer than the edge on a carbon steel blade.
High carbon stainless steel is a relatively recent development that combines the advantages of carbon steel and stainless steel. The higher percentage of carbon allows the blade to take and keep a keener edge. The most desirable type of blade for general use is taper ground, meaning that the blade has been forged out a single sheet of metal and has been ground so that it tapers smoothly from the spine to the cutting edge, with no apparent beveling.
Full tang, meaning the continuation of the blade from the tip of the knife all the way down to the end of the handle, is preferable to partial tang. In some knives there is a collar or shank, known as a bolster, at the point where the blade meets the handle. The bolster helps balance the knife and protect the hand from accidental slips. It is the sign of a well made knife.
Sara Moulton is the "Good Morning America" food editor and host of the PBS show, "Sara's Weeknight Meals." For more great recipes from Sara check out her website or follow her on Twitter: @saramoulton