Hardware-locked protection options

Hi all, a quick question: when you generate hardware-locked activation key,several ID (4 at my version of compiler).- which choices for system ID should be preferred (being both safe and stable)?

Some people reported to me that their activation keys stopped working (system ID changed) - which of the options can result in system ID changing (is it MAC address)?

The MAC address can be the culprit because this MAC address can change depending on the connected network. Don’t use this option unless you know you are sure end users only have a desktop computer (for instance, computers in a school room).

Thanks - I indeed used it accidentally.
The other ones should be robust I guess?

At least, the other ones don’t change unless you change the hardware