Ask the prospective shops if they use "Hexavalent" or "Trivalent" plating. The chemistry is different. Hex is mor hazardous and expensive, and surprise--Better. Trivalent is becoming more and more common, and while it can be done well, its not quite as good.

When you find a shop that still does Hex, its a pretty good indicator that they perform good work and have pride in their work. Think of Tri as cutting a corner, if they cut that corner, what OTHER corners do they cut???