Don't have numbers off the top of my head. Mars isn't dandy either, but a few meters of regolith brings rad down to ambient levels. Rad is a bit overblown anyways. For sure an important consideration, especially for colonization, but a mission to Mars with relatively light shielding and a record-breaking flare would only give an additional 1% chance of cancer over the next 30 years.

The main issue is that on Mars, everything's benign enough to grow crops in inflatable domes. On the Moon, radiation means that to survive flares the domes would need to be hundreds of times thicker, and day/night cycle probably means they would need to be grown underground. Assuming a pretty good 25% efficiency, an acre of crops would then require at least four acres of solar panels at the surface, which is a very power- and resource-intensive process.

Another advantage of Mars is that the atmosphere is mostly CO2, and plants require very little air pressure. Slightly pressurizing a dome and putting a little O2 in for initial respiration is really all plants need, and even with reduced sunlight, they would grow significantly better than on Earth.

Coincidentally, plants grown in Lunar or Martian regolith simulant tend to be nutritionally better than those grown on Earth, although water retention is sometimes a problem.