Living in a house or a building, the task of installing appropriate cables for any device could be done easily. The best example are power plugs since the structural installation provides different spots for easy placement of the devices. Once the cable is plugged, there's almost no limitations on speed, current or voltage gaining in stability and keeping the aesthetics. Other analogy for their closeness are water tubes, they are under the floor or inside other walls and the tap goes where it should be.
A straightforward idea is to start building homes with standard installation for electricity and computer equipment as the state of evolution demands. Ethernet or other connections could change and that could be solved simply by exchanging the socket with a standard size and a minor installation.
Cable provides more speed, no perceivable lag and more overall stability without doubts. The security increases considerably as your modem doesn't irradiate every packet of data to the air toward every place across walls and your body included. Safe or not it's a good question with a very difficult answer as every unique organism has billion pieces and possibilities of interaction, although with a cable you would need really high power to create strong magnetic fields by electromagnetism. If the cable picks up a tiny metal clip inside a common home it might be incredible.
Wireless consume batteries as it needs to irradiate energy toward the environment, an energy that can be obviously measured with equipment and follows the inverse square law. So the energy is inversely proportional to the square of the distance, with the emitter location at fullest exposition.