Layout Generator, some perlins, a nice radial grad for the mountains or craters, maybe a bit of voronoi... Erode that shit and you have a nice little mars scene. I'm gettin' inspired.

Venus - yes. Mars - no.

Venus has:
atmosphere
plenty of solar and wind power,
is closer
has a similar temperatures to that of desert on earth
magnetic protection
Higher level of gravity

Mars has:
Ground
Possibly usable water

In ∆V terms, Mars is closer than the Moon. From low Earth orbit one-way to Mars is 4.3 km/s + aerobrake capture, deorbit & landing, vs. 5.7 km/s to land on the Moon. While the ubitquitous perchlorates in Martian soil are poisonous, perhaps they're also a useful source for the climate engineering greenhouse gasses.

To be honest, it doesn't make much sense living at the bottom of a deep gravity well if you can avoid it. It's just 4.9 km/s to the orbital vicinity of Ceres, which orbits at the distance where there are plenty of volatiles (Ceres's crust is "wet" olivine, 25% water) but still enough solar energy to spare nuclear fuel requirements. And where there's water there's oxygen and chemical rocket fuel. Once robotic mining/refining/3-D printing is up and running, the only things that must be lifted from Earth's surface are humans, biological samples, and high tech parts that require higher tolerances.

If we don't squander this civilization with runaway greenhouse and fighting over resource scarcity, someday there will be fleets of autonomous solar sails slowly ferrying refined materials to construction locales in the Belt. If He3 is abundant enough out there for fusion, then our descendants will pelt Mars with enough comets to restore an atmosphere long lost to the solar wind.