Technician A is correct.
It’d be wrong for technician B to say that one disadvantage of fiber optics is that they can only carry a limited amount of data and at slow speeds. Actually, the bandwidth that can be transmitted over a fiber optic cable as compared to other transmission media like metal cables is much greater and is its most significant advantage. It is however, safe to say that the cost between a fiber optic cable and a copper cable is higher. The cost itself of installing fiber is relatively higher. Fiber Optic Cables are also very heavy and modern ones can contain up to a thousand fibers in a single cable.