A few points:
Content yes....but they can't provide a sky (not a real one anyway)
One could make the same argument about L.A., at least during smog season.
Seriously, though, people in Norway or Alaska go for months without seeing a daytime sky, just starry nights, same as in a space station. I imagine a space station could be easier, since you don't have the cold. It's all what you're accustomed to. In an Issac Asimov novel, people in future societies have roofed their cities and are actually afraid of the open sky, because no one grew up looking at it.
but seriously would you want to live on a space station or on a planet.
It would depend on the planet. I imagine living on an relatively inhospitable planet would be no better...and perhaps worse...than living on a space station. You're still stuck inside in domes or something, you have confined space to deal with, you possibly have something like dust storms or corrosive poisonous atmosphere (e.g. Venus) or extreme cold to contend with, and living in a space station would be preferable (better natural light, possibly more space if construction conditions on the planet were more difficult than construction in space, more reliable power supply, etc.)
It varies wildly -- we know of colony planets with as few as a couple thousand people... and others with billions. In the first moves of the war the Kilrathi captured 153 frontier systems with a total population of 28 billion... that averages out to something like 180 million per planet. (In a war where multiple trillions died, there had to be some pretty serious populations on the worlds affected by the fighting.)
You make the point about widely varying populations, but then imply that the average colony has something like 180 million. I think it's very deceptive to use a mean population, since planets do vary widely, and the average is likely skewed by a very small number of earthlike planets with huge populations. Consider our solar system. There's two, maybe three planets that would be habitable by 27th century standards, probably, and maybe two or three more large moons. Only one is "earthlike", and that planet currently has a population of 6 billion. Imagine we managed to get a Mars colony going with ~1 Million, and then everything else you could imagine colonizing you only get a few tens of thousands (trying to build any kind of bigger population complex on Mercury, Venus, or Europa or something would be prohibitive even with advanced technology because of environmental hazards as well as available size of the planet). The average population in our solar system would then be about 1 billion per colony, but the median population would only be a few tens of thousands. In the case you cite, the Kilrathi could have easily captured four earthlike planets with 6 billion people each...and then 149 mining colonies each with only a couple tens of thousand people each.
On the other hand, we know that space stations can be built in the 27th century to support tens of thousands of people. In a way, it's easier to build a big space station than a big colony on a planet with a hostile environment, because, assuming you can get the materials into space, construction is much easier in microgravity.