There is no single steel that is perfect for every situation, but I have found AEB-L to be an ideal choice when applied on small to medium outdoor knives. It has a unique combination of toughness, edge retention, and ease of sharpening not often found in other simple stainless steels.
The reasons for this get fairly technical, but I will try to put things into layman's terms.
On a molecular level, carbides are what give stainless steels their edge holding capabilities, but carbides also make a steel harder to sharpen. AEB-L differs from most simpler stainless steels in that it forms very small carbides when heat treated and has a very fine grain structure. Since the carbides are small, they are easier to sharpen, and since the grain is so fine, edge stability and toughness get a boost. Because of these advantages, AEB-L can compete with more complex "super steels" but at a much lower cost.
For an even more technical look at what makes AEB-L the wonderful steel that it is, custom knifemaker Devin Thomas has some great info on his site, quoted here:
Few know what AEB-L steel is, and those that do, only have heard that it is similar to 440B or 440A. The only similarities between AEB-L and 440B or 440A is the amount of carbon. The fact that AEB-L has only 12.8% chromium by weight compared to the 16-17% in 440A and 440B makes the steels quite different. AEB-L is more similar to a stainless 52100 than 440A...
AEB-L naturally forms what is called the K2 carbide, the harder of the two chromium carbides, compared to the K1 carbide, which is formed in steels such as 440C. The K2 carbide is about 79 on the Rockwell C scale, compared to 72 for the K1 carbide. Through proper heat treatment, AEB-L has fine, evenly distributed K2 carbides. AEB-L lies almost perfectly on what is called the "Carbon Saturation Line", which means that all of the carbides formed are precipitated carbides, not primary carbides like are formed in 440C, and there is more carbon and a similar amount chromium in solution as compared to 440C. Primary carbides are very large. So, through a balanced composition, AEB-L has excellent toughness, edge retention, workability, ease of sharpening, and ease of polishing.
Roman Landes and John Verhoeven have both done different tests with AEB-L. In CATRA testing Dr. Verhoeven found AEB-L to outcut 52100, 1086, and Wootz damascus. He also found AEB-L to be able to take a smaller edge radius than 52100 in controlled sharpening tests. Roman Landes found AEB-L to have greater edge stability, toughness, and wear resistance than 52100. Edge stability is a property that describes a steel's ability to hold a finely sharpened edge. 52100 is one of the most well respected carbon steels, and is well known for its small carbides, high toughness, and high edge stability, so it's impressive that AEB-L was able to beat it in these categories, while also having greater wear resistance and being a stainless steel. Many users have reported that AEB-L sharpens as easily as any other carbon steel they have used.
It is for all of these reasons why we have found AEB-L to be the preferred stainless in our knives. After testing the steel extensively, we know it has what it takes to stand up to the rigors of outdoor use, and it will do it with a smile!