And while we can breathe the air and not get radiated to death by the sun (during the times its visible) on Antarctica, it's in other ways much less hospitable than places like Mars. Mars has a relatively normal day/night cycle which [presumably] means no T3 syndrome like many suffer in Antarctic winters. It also gets warmer on Mars than it does on Antarctica. If not for the atmosphere, many days would be quite pleasant. The low density atmosphere also means you don't need to worry about things like storms (one of the main things that was completely faked in 'The Martian') - the most brutal storm on Mars would feel like light breeze. And it has to be said, even if for just an entertainment factor - low g!
There's also the drive for discovery. You may make some interesting discoveries in Antarctica (if you were allowed to engage in operations that would allow such) but they're going to generally be 'terrestrial' in nature. While this may end up being true of Mars as well, for now no one entirely knows. We're still making revolutionary discoveries on the Moon's composition and we have actually landed on it! It's very hard to know what you don't know, but the one thing that blazing into new frontiers has shown time and again is that there's an immense amount we don't know that we don't know - and I don't see any reason to think that this is no longer the case.
In many ways I think Mars has the potential to be another Earth. Different in many ways of course, but also similar in breadth and possibility. Whereas Antarctica's potential is something rather different, but altogether inhibited by rules and regulations in any case.
That's an aside. With my point I was getting at two things. The first is literal size. Mars is smaller than Earth of course but it's actually near identical in size to the land area on Earth. It's really big. And there's no major obstacles in the way of exploitation. For instance like the ocean and weather irregularity on Antarctica. And there's also likely an extensive array of mineral deposits on Mars. The surface itself is red from iron oxide, aka rust. Basically if you can imagine it, you can build it. This really opens the door for entrepreneurship like nothing before. Would it be possible to have a domed forest on Mars, or eventually even domed outposts that begin to resemble cities? I don't see why not. There are also even bigger picture terraforming ideas. At one point in its history Mars likely very much resembled Earth. The loss of its magnetic field exposing it to radiation and stripping away it's atmosphere likely played a major role in its decline. It's possible that we could create an artificial magnetic field on Mars in a variety of ways. Again - potential.