I grew up in Colorado, lived in Seattle, spent time in Utah, and now live in Boston (I know, it makes no sense - it is temporary). I have skied nearly all of the Colorado and Utah resorts repeatedly. There is no question that the skiing in either place will far outshine what you are used to. Both CO and UT have great snow, great weather, and great terrain.
Forget about skiing for a moment (I know that is hard to do). You are comparing apples and oranges. SLC and Junction are vastly different places. SLC is a city, whereas Junction is a small town. Both I think can offer a tremendous quality of life. Junction is close to many great things. The Grand Mesa (which is awesome and highly underutilized - tons of alpine lakes) is right outside your door; the Black Canyon is an hour away; the Colorado River flows right through town; Fruita (great mountain biking and hiking) is right there too...the list goes on.... SLC of course has the Wasatch, and those peaks are literally right in your backyard. Tons of good stuff there as well.
Big city vs. small town? When I think of this dilema, I always wonder about things like culture, restaurants, intellectual stimulation...etc. Yes, there are some small towns that have it all (Telluride and Park City were two great options you mentioned), but those towns are cost prohibitive to most. In my opinion, SLC does not have the culture of Boston or New York, or even Denver or Seattle, but it certainly has more than Junction. (On the other hand, from Junction you can drive to one of those "perfect" small towns whenever you like. So if seeing a concert is, for example, a once a year thing for you, it can be available).
How important is topography? Both are high desert locations, but the vertical releif in SLC is prolly better than Junction if you want to see huge snowcapped mountains out your window. However, Junction is beautiful in its own way too (think fantastic eroded mesas). You just have to see it to decide on this point.
Both are going to have great outdoor activities. There is no need to wade in the the "superiority fight." One thing to note that no one else has mentioned is that Junction does have a ski area close by - Powderhorn. It is small, but can be quite good. It is only a few minutes away.
How important is proximity of skiing to you? SLC obviously wins in this department, as several world class resorts are just minutes away. As noted above, Powderhorn is close to Junction, but the other Colorado resorts will require a drive.
Do you love those ski towns you mentioned? Park City is cool, but it is the only one in Utah. If you want a great weekend away in a small ski town, Telluride, Aspen, Crested Butte, Steamboat, Vail/Beaver Creek, Silverton, Durango...etc. are all within striking distance.
People? Well, what can I say? There is obviously a large religous and cultural contingent in SLC that doesn't exist in Junction. I can't and won't judge that in the least, as I have not experienced the influence on someone who lives there. I will say that SLC is the only place where I have been approached on the street corner repeatedly by people spreading the gospel. They were all nice, and it didn't bother me much, but I did find it odd. More importanlty, I have heard stories from friends who live there that there can be a bias against non-Mormans, and that such bias can affect one's chances of upward mobility. I don't know to what extent this is still true or whether it would apply to nursing. However, it strikes me as crucial to find this out sooner rather than leter. That said, I have found the people in both towns to be great.
Drinking laws? Non-issue.
I don't know about hosuing costs, or job prospects, but obviously those are HUGE factors. I would assume Junction is cheaper, but have no info to back that up....
In the end, you have to see both places, and consider all the factors. If you want to confuse the issue, consider other great places. If you want a city, Seattle, Denver, and Vancouver are all awesome. If you want a smaller town, consider Durango, CO, Bend, OR, Glenwood Springs, CO, Truckee, CA, Whistler, BC, Bozeman, MT, Fernie or Nelson, BC, or any other great towns in the west. They are all different, and all have much to offer.
Good luck. It is a wonderful choice to have.