Elon Musk: We're going straight to Mars. The Moon is a distraction. (2025)

In terms of rocketry Mars could be a little closer than the Moon with Starship because Mars has all the elements to make oxidizer and fuel.

The difficulty with Mars is latency. You get opportunities to go there every 26 months and then spend 6-9 months in transit. If you need spare parts you could be waiting for years. You want all the technology you depend on to be completely boring.