SLC, easily. And not just because I live there.
For starters, the climate's a lot better here. In SLC you can actually get snow (with access to several high-quality ski resorts). Las Vegas and Phoenix are in the middle of a desert, where snowfall is rare, and the summers are excruciatingly hot.
Second, Las Vegas and Phoenix have become massive cluttered sprawls, while the Salt Lake Metro has been fairly well planned-out in comparison.
Third, there are tons of high mountains here with lots of mountain ranges, which have access to skiing (as mentioned), hiking, and resorts.
And last, despite what outsiders think...SLC is actually quite liberal. certainly tolerable for someone like me.
Do you mean the Vegas strip, or literally the city of Las Vegas? I've only been to the strip and it was interesting. I'd probably choose Salt Lake City, though.
Hate to nitpick, but the strip technically isn't actually in Las Vegas - it's in the CDP of Paradise.
Anyway, I encourage more people to come on down here!