What is the right cable for a new networking installation, copper or fiber? 

Copper cables actually contain copper wires and have been used since decades for telegraphic data and electricity transfer, much before information technology came onto the scene. They are typically heavy and since copper is a good conductor, it uses electrons or the negatively charged ions to transfer data. So, typically, a copper cable comprises a bunch of at least two or more copper wires which are insulated by a non-conductor sheath.
A fiber optic cable is relatively recent, and in fact has been quite a revolution in network connectivity. A fiber optic cable comprises a bunch of glass fiber strands which are insulated by a non-conductor material, and are typically used for connecting networks across long geographical distances. These cables transmit light signals, and we know it travels much faster. They offer a much higher bandwidth and high-speed data transfer, depending upon their type. In fact, they have a large application in connecting the global Internet, telecom systems, cable television, and so on.
Fiber optic cables are nowadays widely used for many applications as they offer several advantages. In fact, if you have an existing copper cable network, and you want to extend it, you can do so with the help of fiber optic cables and a media converter. Copper cables are still used in many electrical circuits. They are also used in networks even now as they are reliable in terms of conductivity, tensile strength, and so on. Copper cables are cost effective as well. But certainly, fiber optic cables are robust, less susceptible to sparking, tampering, and so on, and much more flexible in terms of connecting dissimilar networks. They are the best for industrial areas and long distances.