I don't know why orbital solar isn't discussed more. Folks cite efficiency losses when transmitting to ground, but does it rise to 50% like ground-based?
PS: Orbital solar is an issue due to launch costs, and the fact most electricity is used in the daytime. Solar + battery is also getting very cheap.
Understand that a colony on the Moon isn't there just as a proof of concept. Its there to do something, probably industrial. Running billion-dollar industrial processes only when the sun is shining, is clearly a downside.
Batteries + solar are already cheaper than new nuclear power on Earth over 24 hours. For Mars the reduced sunlight is an issue, but nuclear also faces major issues without ready water and very low atmospheric pressure. Low ground temperatures allow you to dissipate heat, but construction costs would be dramatically higher.
The moon is different due to extended day night cycles. Which also make it extremely unappealing for long term colonization. Trying build a reactor that still operates when ground temperatures hit 127 degrees Celsius is again very difficult.
Out past Mars solar is a poor fit. But, without something like cheap fusion power it’s extremely unlikely giant colonies would be viable anyway.
So in fact a solar panel in space around the asteroid belt (outside the orbit of Mars) gets about the same flux per square as Earth ground-based. If I estimated right.
Anyway, talking space-based solar vs ground-based solar (not nuclear). Due to the twin advantages of less atmosphere to get thru, and no/less night.
Looking at averages is misleading. Clouds and the atmosphere on average reduce this significantly, but that’s very location specific. Near the poles the sun stays at very low angles 24/7 which significantly increases the average absorption. But, solar is a poor fit at the poles anyway.
Mars is 144M miles from the sun, average. The earth is ~100M. That's a difference of about 1.44:1 which puts the inverse-square reduction due to different distances at 2:1.
What does that mean? Mars solar flux is about the same as Earth at sea level. So expect similar solar panel efficiencies.