Mars will kill people. It is not only horribly cold, it has much weaker gravity and is bombarded by radiation. Humans cannot survive on Mars, even if you solve the cold problems and radiation problems, because the Human body is not capable of surviving under sustained lack of gravity.
It took years of research in space to arrive at this conclusion, but I think it is now pretty much a consensus that gravity is necessary for human health.
A tourist destination for short stays, perhaps, but that's about it until Mars gets more mass.
The problem is we do not know how to construct a working ship able to rotate its crew quarters supplying centrifugal force to simulate gravity - despite the Hollywood concepts.
The real problem is lose of sight - it seems the eye parts begin to collapse under prolonged weightlessness leading to eventual blindness if the condition becomes long term as in present propulsion engines mandate for a trip to Mars.
Both the Moon and Mars have adequate gravity - the trick with Mars is getting there and back with one’s eyesight intact.
Both bodies have significant problems with meteor strikes and radiation - the solution for both is to build all the main structures underground, with any surface structures built with water-filled walls to minimize radiation. (The water can be either from underground sources or from catalytic conversion of the soil.)