The black Fetrotech tool is used as a standalone module, i.e. you can use on its own with a dedicated pc, the silver one works in conjunction with pcmtuner.
The black one has a pcmtuner port as well. You can use it standalone (has independent software) or use it with pcmtuner or other devices.
The silver one MUST be used in conjunction with the pcmtuner. Fetrotech will connect with the pcm tuner to get more protocols. The silver one can be controlled by pcmtuner app to access pcmtuner account.
Both can access the vz-performance online tuner account to download VR files, map pack and damaos.