If you care about interference ethernet over power is awful. It basically turns all of your electrical wires into a giant antenna and broadcasts that as broadband noise over multiple miles.

The only reason the things aren't outright banned is the frequencies tend to be sub 100mhz so it only has a significant impact on HF. Still, nasty things and many have been found over the legal noise limits.

If you can I recommend point to point 2.4ghz wifi links. Since wifi is regulated by ERP they have a high gain antenna that usually punches through things better than an omni AP. I've done them through multiple walls from 300-400ft away.