Dear Jürgen! I think I’ve figured out why Nuki is safer than the other devices. 
(I have thought a lot about this.)
What happens if a device is duplicated or cloned? (including serial number, software identifiers and everything else)
If your device is managed by an Apple Smart Hub (hereafter referred to as a server). The server cannot distinguish between the original and the cloned device. It sends both devices the data needed for unlocking.
With nuki, this cannot happen because the device itself stores everything. It does not need a server. Right? The wifi enabled version just passes through the nuki servers but the actual data storage is done by the device itself. Am I right?