> It sounds like one of their main arguments is that it would be a less difficult and/or dangerous way to get some experience with medium to long-term human habitats on other planets, partially in preparation for a Mars trip.
I'm still not sure why we're interested in inhabiting Mars. Virtually no atmosphere and one-third of Earth's gravity means that humans will always have immense difficulty colonizing the planet. People who lived on Mars for any extended period of time, for example, would have huge difficulties in adjusting to Earth's gravity, if they could at all. People would always have to live in pressurized habitats.
Meanwhile Venus has a thick atmosphere and a much more Earthlike gravity. There's certainly huge problems with Venus (most obviously: it's very hot) but I can at least imagine with time and technological advances we could terraform the planet to be suitable for Earth life - all the raw material is there.
This is not to say, of course, that establishing some kind of manned scientific facility on Mars wouldn't be worthwhile. But long-term habitation? I just don't see it.