Nicholson is what I use(mostly) and they seem to hold their edge for quite a while when working junk steel. I say junk because the blades I forge are out of coil springs, lawnmower blades, etc. I get them at the local hardware. I rarely use files/rasps on wood because it hogs so much material off. I just get it close with the belt sander and use paper by hand. A trick that Gene Wensel told me long ago is to drill a small hole in a golf ball and jam that onto the file handle. Makes a really comfortable tool. Chalk rubbed onto the teeth help keep the metal shavings from building up as well.
Bob Urban