I must say that all this talk of bad air in the front range seems a bit off to me. I know it looks bad, but its waaay better now then it was 15 years ago. I grew up in Vail and remember coming into denver and seeing a nasty big ole dark brown cloud hanging over the city every time. Its more of a wispy white smog cloud now, and while its definetly not the clear air of the mountains, its not that bad. Most other large cities are far worse. There are crappy days when the wind blows it up onto the mountains but hey.
As for which is better, its a toss up really. I have experienced both places. I have lived in Boulder for the last 5 years, and have spent plenty of time at my moms in Vail over that time too. I will say that I am through with Boulder, as its changed alot for the worse since I moved here originally (or I have changed for the better/different). The crappyness at CU is also reflecting itself in the general community, as its turning into too much of a yuppy town for people who think they are liberal and hippies (but really aren't in any way). Just to show, despite asking plenty, I haven't gone on a single date with someone who lives in Boulder in five years of living here. This is despite that fact that there are more girls then guys in the age group between 20-25 (I'm currently 24). Not sure about elsewhere, but Vail has its problems too. My chances for love aren't any better there as the ratio sucks, its expensive, harder to find work, and everything is far away (hence more gas used, which is a double hit because of the significantly higher gas prices in the mountains compared to FR). I have been working some up there at one of the shops, and it is amazing to me that almost every woman who comes in has a Boyfriend or is married.
I will say that after experiencing boating in both places, that I would choose the mountains over the city most days. Yes there is quite a bit of good stuff in the foothills (Bailey, Clear Creek, Saint Vrain, Poudre, hell even the Urban boating can be good if you can deal) but they tend to be a long drive. Vail has just as good of stuff around as the front range, but its closer in general.
However, there is one clencher that seals the deal for me. If you are a skier that likes to go more then once a month, living in the mountains is the only way to go. I grew up in a house that was a 15-20 minute bus ride to the base of Vail, as such was rather spoiled in that respect. Moving to Boulder ruined skiing for me (I will say I was getting a bit burnt out on it anyway). Sitting in 4 hours of stop and go traffic to go to a crowded mountain is not my idea of a good time. If you can make it on the weekdays its better, but still not really worth the drive unless you can stay for more then a day. Other then that, I often find myself wishing I was in the opposite place. In the end, I think I would choose the front range, as it has most of what I want and need. More to do, stuff is closer, more choice, and it just takes a bit more effort to find the cool people. The skiing thing is over for me anyway for now. I haven't skiied in over a year and don't regret it a bit. Ok, end of rant.