5160 is a very tough steel, used for car springs at lower hardness. At typical knife hardness levels, 55ish-RC, it makes a good chopping knife that can take a lot of abuse. In a smaller knife, you really wouldn't notice much difference in performance as compared to any other quality carbon steel. My personal favorite for axes and chopping knives.
1095 is a very good all-around alloy. I have small personal fixed blades as well as 10" chopping knives in this steel, it's quite good in any size blade, as long as the heat-treat is done well.
1075 is another good steel for large outdoors tools, very tough stuff, but is not as good at edge-holding as 5160 or 1095.
D2 is considered semi-stainless, with only about 12% chromium in the alloy. Takes and holds a really good edge. As was said, it's not really difficult to sharpen, it just takes a little longer. It's best not to let it get too dull in the first place, regular touch-ups will be far more effective, although this is true for any alloy.
AUS-8 is a Japanese alloy generally similar to the 440-type stainless steels. Although it is another good all-around alloy, it's not held in particularly high regard by many, especially around here. But, this doesn't mean there is anything wrong with it. It's a utilitarian steel, not a boutique alloy. It is reasonably tough for a stainless steel, edge-holding is about average, and as noted, it is generally pretty easy to sharpen. I like this one best in folders.
There's no such thing as a bad knife steel. If an alloy can be hardened above about 54-55RC, it will make a perfectly serviceable knife. Edge geometry and heat-treatment are more important than the alloy used.
