AUS-8 is excellent Japanese steel. Properly heat treated, it holds a keen edge well. Spyderco folders used it a lot. My Spyderco Endura in AUS-8 took an effort to get sharp but maintains the edge well. 440 comes in various configurations. 440A, 440B and 440C, from less to more carbon. As stated above, 440C is excellent and Randall uses 440B. When a manufacturer mentions 440 steel, they usually mean 440A, as they'd let you know it if they used the others. 440A is about the minimum for quality edge holding in a knife used often. Heat treatment means everything in knife steels. A properly heat treated blade in 440A is much better than a poor heat treatment in 440C.
Joe