@jbuhl - The choise is actually pretty simple - ask yourself what is the main metal used in the plug...
- for best results - it should be PURE copper
- it should not be any other material, such as..
- beryllium copper, teryllium copper Bronze or brass
- they are NOT copper
- they are copper alloys
- it can be plated or just bare copper
- Bare Copper will tarnish so some kind of plating is advised, otherwise they will require perodic cleaning
- my preference is Silver plated copper
- because it has higher rates of conductivity that other plating metals
- gold plating is the next best metal commonly used
- rhodium or Platinum are among the worst metals for plating based on conductivity
- any other type of plating will degrade performance
This is all based on the Conductivity of the metal
- Silver is at the top - at up to 106%-107%
- PURE anealed copper is rated at 100%
- THIS was the "benchmark" for all other ratings
- OFC copper is around 101%
- the more advanced copper like UP-OCC copper is 102% - 103%
- beryllium copper, teryllium copper is around 40% - 65%
- Bronze or brass are down around 30%
What does the metal impact?
- details and clarity
- dynamic performance
So when you are buying plugs think about them in relation to the attributes of the metals listed above.
Buying expensive brand names may not get you the best plug either
I have tried many plugs and the two I recommend and use are
- Sonar Quest Silver plated Copper
- these are very well made
- their pins are very flat for the best connection
- they have a heavier amount of silver plating that most others os the plating will not easily scratch off with use
- Vanguard Silver plated Copper
- A good amount of plating
- but the pins are not quite as flat
Both are available from Ebay for a reasonable price
Hope that helps - Steve