I would personally not suggest any shim as they create a false sence of security and as such some people take less care on attaching the heatsink with them. Shims also effect tempratures and the conductive ones can even short out the bridges if they move. A shim is not exceptionally thick and if roughly handled or dropped can distort and lift the heat sink away from the CPU.
If you had to obtain one of those shims I would choose neither as copper conducts electricity and if a shim made of this material like those in your picture comes in contact with your bridges it is not good.
The risks are far greater than the advantages imho
Shims can really help with something like a globalwin. A copper shim will raise temps quite a bit, but the nonconductive shims don't do it nearly as bad (1-2C) and will not short out the bridges either.