Why Are Lunar South-Pole Landing Sites Harder to Reach Than Equatorial Ones?

Several lunar missions are aiming for regions near the Moon’s south pole, where permanently shadowed craters may hold water ice. But landing there sounds more complicated than choosing a flat spot near the lunar equator.

Is the main difficulty the steep, uneven terrain, the long periods without direct sunlight, or keeping a reliable communications link with Earth? I’d like to understand which constraints matter most when mission teams choose a landing site, and how they trade scientific value against the risk of getting a lander down safely.