Electronic – Earth ground to dsub9 shell

Any long cables with RF clocks/data will radiate noise and when connected to AC ground could also radiate via AC cable from path ground loops.

Smart idea is make generous use of common mode chokes for interface cables and DC outputs to raise impedance of the common mode signals from AC ground.

Beware that Hipot testing of AC/DC PSU may cause failure on secondary port when grounded. This is due to dielectric breakdown of Hipot from primary to secondary. Floating secondary is easier to protect if there is capacitive leakage and tester uses fast rising input. In this case modify Hipot tester to avoid discharge surge that would destruct PSU by using a current limiting series resistor.

Leakage can be minimized with prudent gaps, quality caps, and moisture protection on conductors. (moist dust causes leakage)

Short answer is Yes.

The differences in geology (chemical, water content, magnetic (Earth's magnetic field), electrical disturbances (including lightning), physical stresses) mean they are different.

Remember the Earth is a rubbish conductor (mixture of insulators, semiconductors, conductors and liquids in random proportions from place to place) so if you tried to harness this I believe you won't get much consistent power.

You might get a huge magnetic input of power during a solar storm due to the changing magnetic field of the Earth as it interacts, but until we can store such unpredictable power, it is of limited use.