There is much debate over which spokeshaves are better. There is some argument that the two types are designed to carry out slightly different tasks: the wooden spokeshave being for the removal of wood quickly, and metal ones most suitable for finishing cuts.
It is more of a personal choice as to which works best for you, it is often just what you get used to and practice with. As some metal versions often need working on before they can be used efficiently, they are easily mistaken as bad tools. However, metal spokeshaves are also much more widely available.
Wooden spokeshaves are often made by the specialists who use them, like chair makers. Often these specialists sell their own wooden spokeshaves. There are also kits available to enable you to make your own spokeshave.
