I am a much bigger fan of Mercury, though it is less popular (http://einstein-schrodinger.com/mercury_colony.html previous discussion https://news.ycombinator.com/item?id=5734333 )

Mercury is indeed interesting from a colonization standpoint, but it's really less interesting than Mars from a science standpoint. Mars could potentially answer fundamental science questions around the origins of life.

That first link was a very interesting read, thanks for sharing!