Well, IMO, a boot-knife is a weapon (a tool for taking life), or a display case piece.
Dont know about the Nieto knife, but the S&W should be fine for either purposes. it has a point, it has an edge, and it appears to have a solidly mounted handle. Steel is decent, or will be if the heat treat is decent. But, as a dagger, its not so much a cutter as it is a stabber, so again, its pointy, it has an edge. Thats all ya need.