Here's the scoop:

PLATINUM (the heaviest)

• requires special tools
• most costly per troy ounce
• maintains strength for intricate delicate designs
• can be repaired but requires professional polishing
• usually rhodium plated

18 & 14 Karat Gold (less heavy than platinum)

• less costly per troy ounce
• works well for more massive rings
• can be repaired
• usually rhodium plated

Sterling Silver (lightest weight)

• least expensive per troy ounce
• great for large pieces and hollow pieces
• repair of silver is time-consuming and demands great skill - don't expect good repair of silver to be cheap
• clean and polish like sterling tableware
• mass manufactured pieces are sometimes rhodium plated