Cadmium plating is illegal now I think... very toxic!
Zinc plating is cheap, looks good and does the job. However, Stainless steel is better. Most fasteners are available in stainless now and it looks lovely and lasts too. OK, if you are a real originality freak it might not be what you want, but it does work well. Zinc is best for originality. Try and find a company that does 'Barrel Zinc Plating' if you take that route - you can chuck every fastner, chain adjuster, gbox adjuster, spacers etc all in the same tub and get them plated for about £25!