Mars has a lot more benefit here, in that it has a normal-length day. Much better to reliably have sunlight for roughly half of every day than to rely on a few polar areas that are in sunlight most of the time. The equator of the Moon is more suitable for other reasons, so what are you going to do, put the solar panels at the poles and run long power lines down to the equatorial regions where the power is used? Nah.

Mars is better for solar power because you won't need nearly as much battery capacity, as you get light on a ~24 hour cycle same as Earth. The Moon with its slow rotation is much more challenging.