By pyro I must assume that you are asking about a staining developer. By "works best" just what do you mean? Finer grain? Xtol is a fine grain developer.

The answer is that a stain image can never have as fine grain or accutance of an ordinary image. The reason that this is true is that the stain/dye migrates away from the silver halide grain during development. The result is that the apparent size of the grains is increased by the larger dye clouds. The dye cloud also masks fine detail. This can be easily seen with the use of a microscope. Each silver grain is surrounded by a stain halo. This is why staining developers are not recommended for 35mm films.