Your best bet is to read up on as much as you can find on both. Tony is right about nickle though, it looks great, but is more porous than zinc, and is thus higher maintenance to prevent corrosion of the substrate. Zinc produces a sacrifical layer of oxide over the top and as such is the choice of nearly every OEM manufacturer for durability v. cost. Most OEMs use a final chromate process; gold-ish or blue-ish hue to further protect the base material. Caswell has many chromating color processes to choose from as well.
Cheers, Dan.
