But that's kind the point: why would I want to colonise/terraform Mars? The only reason is: if there are resources there, enough to justify making a colony there. That however happens (in my case, maybe I've been unlucky) in one game out of three. Unless I use SM mode that is.
Plus, for the pre-terraformation colony to be of worthwile size, you need thousands if not tens of thousands points of infrastracture. And if you want to have both mines and terraforming facilities you'll need at least that much. That means a lot of industry being used and a lot of freight. Not counting terraformers that is. On the other hand terraforming ships are a very good investment, becouse they can make planet habitable before you establish any colony there. So no need to send infrastracture. Also, terraforming ships are much less micromanagy.
I guess that if you're playing a game where Mars is a very good mining outpost, then yes, definitely infrastracture is the best way to go about it. But after Mars terraforming ships are just too good. Just my opinion thou.
As for overcrowding, I'm not sure what the way population stops or doesn't have to do with it. I mean, the reason they are unhappy is becouse the place is overcrowded, ie, they can't have children becouse the life support won't handle it. In which case it doesn't matter whether the growth stops or not - they are still feeling overcrowded.