Mars, much further away than the Moon, much greater gravity well, no magnetic shield that could protect a terraformed atmosphere (its core is dead).
So why are we hearing about its potential colonisation so much?
Because the dream is a product. It can stay indefinitely in "development" while earning its promoters real world goodie tokens. They get publicity pandering to myths we all grew up with as kids while being able to postpone the dream delivery a couple of decades so as not to be called on it.
Maybe humans will one day create sustainable habitats within the solar system and beyond. I certainly hope so. But not before we deal with a severe resource, energy, pollution and over-population problem here on what is by far the most interesting "rock" in the universe that we know of.