Any of the steels Buck uses are capable of getting extremely sharp. Most any decently heat treated steel is. You need the right media and techniques for the steels but by and large they can all get there. For the most part, one steel type does not have the, um, edge over another in terms of being able to get very sharp. Again, if it's well heat treated, not talking about gummy Pakistan car bumper steel. For sure, some steels sharpen up easier than others, but if you have the right tools and the proper technique, you can get pretty much all of them extremely sharp. As
David Martin
has so rightly said, even low grit edges can shave arm hair. And as another poster said, facial hair is an another matter. The key difference here being comfort. You need an extremely thin, keen edge for comfortable facial shaving. I don't even bother.
The different steels shine in their edge properties after they are sharp. Some will have long lasting edges, some will be tougher, and so on.
Factory edges, as sharp as they so often are, are also often not durable. They've often been weakened and it'll take a sharpening or two or three to really realize what your knife's full edge properties.
The blade shape itself doesn't really affect how sharp it is. Provided you have good edge geometry, the edge will get sharp. But the blade shape can enhance or inhibit overall cutting performance.