The answer depends on what you are doing.
Foam shims work best with foam wall panel shower systems such as Kerdi board. The foam shims can be used for pinning floors when pouring self-leveling for tile and other hard surface flooring materials.
The honeycomb plastic shims work best for installing cement boards, Hardie backer boards, drywall, and other hard materials. The honeycomb shims can be used for pinning floors when pouring self-leveling for LVT and other soft surface flooring materials as well as tile and other hard surface materials as the honeycomb can be filled with the self-leveler to provide a 100% hard surface for finish flooring materials.
The foam shim kits are available for purchase online at Built With Foam
The plastic honeycomb shims are available online at Built With Foam.