Photovoltaics are not nearly as efficient, unless they use expensive materials. In order of decreasing efficiency (and cost) are:

Monocrystalline silicon = 23 percent efficient
Polycrystalline silicon = 15 percent
Amorphous silicon = 7 percent

These cells also degrade with time, losing 50% of their efficiency with exposure to sunlight. Attempts to increase efficiency of amorphous silicon PV have employed doping compounds like Gallium arsenide (GaAs), copper indium diselenide (CuInSe2), cadmium telluride (CdTe). Mass production of these types of cells on the scale of the ARMXER Orbital Skyhook Infrastructure would likely lead to resource depletion. Also, degraded cells have to be replaced, whereas mirrors may only need to be polished or cleaned (easy). One hybrid solution is to use mirrors to concentrate solar energy onto a PV panel. This way, a large inexpensive mirror collects the rays, while a smaller more expensive PV panel converts them to electricity. I've heard of efficiencies of 30 percent for this method, but I can't find any references.

Basically, I just prefer the solar concentrator system, because it is recognized to be inexpensive, and its quite easy to predict performance. It's just a choice.

My design of an ARMXER Orbital Skyhook Infrastructure calls for 62.5 million metric tonnes of powerplant components, half of which would consist of aluminum mirrors, and the other half structure. The mirrors would be polished 1/16-inch thick aluminum plates 5-inches wide, with a good specular finish, and vapor deposited with a 1500-2000 angstrom-thick aluminum coat. The structure might not be aluminum, so the structural mass estimate is a guestimate. Nevertheless, alot of aluminum would be needed for the solar powerplant. If you check my geometric launch schedule, annual launches of powerplant components would eventually increase into the multimillion-tonne range. According to the International Aluminum Institute world production of aluminum is about 20 million metric tonnes annually. So to prevent shortages, the total amount would have to be anticipated, and parts manufactured years ahead of time. It is hard to estimate world demand for Skyhook launches, but it might be safe to guess that the world's richest 1% might pay for at least one ride into space each year, but demand might be less predictable for poorer populations. Still, as stated, a 62.5 million tonne powerplant would have a minimum of 31.25 million tonnes of aluminum mirrors, diverting 781,000 tonnes of aluminum from the open market every year, for 40 years. This is achievable, I think, but only if we divert resources ahead of time, otherwise as the launches are scaled up we would be diverting several million tonnes of aluminum annually, which is an unacceptably large fraction of world production. I should point out that with the ARMXER Orbital Skyhook Infrastructure, nearly everything we launch, STAYS in space, and works for us to facilitate future launches. Not like rockets.