I was never especially wowed by SLC when I used to visit there semi-regularly though the nearby skiing is hard to beat.
One issue I have with a lot of smaller cities with walkable cores is that you run out of choices pretty quickly. I'm familiar with a number of places in that vein and they're fine to visit once in a while but I think I'd tire of them as an example of "city living" pretty quickly if I were looking for that sort of thing.
I never got bored with lunch for the two and a half years I worked downtown in SLC. Now that I'm in SF I am having a hard time finding replacements for some of my SLC favorites -- one advantage of a smaller city center is there's more variety in less walking distance. SLC has good Asian crossover, Chinese, Vietnamese, Mexican (good stuff like mole), American, Thai, Italian, hipster, burger, pizza, sushi, etc. options all close to each other. Some of that is fairly recent.
For lunch, I'm fine with a handful of options. Heck, I was good with the handful of decent lunchtime restaurants in downtown Nashua NH for a number of years. But for the tradeoffs involved with actually living in a city, I want a lot more than a reliable rotation of restaurants.
Specifically with respect to SF vs. SLC though it's somewhat general to coastal big city vs. relatively prosperous smaller city:
- SF is going to be a lot more crowded, noisy, less clean, obvious signs of poverty. Nothing you can really do to address it other than be aware that some areas are best generally avoided.
- On the other hand, SF has a lot more culture, restaurant variety, and is just a more interesting urban environment than SLC. So, basically, take advantage of that. SF, more than even most larger cities, has a huge number of interesting nooks and crannies to explore.
- Generally speaking, smaller cities often do have some degree of walkability in a central core but you're still crowded in to some degree while you lack the variety and opportunities that preferred large cities have to offer. (I'm not personally much of a fan of smaller cities. I think they tend to have city disadvantages without giving me offsetting benefits.)
One issue I have with a lot of smaller cities with walkable cores is that you run out of choices pretty quickly. I'm familiar with a number of places in that vein and they're fine to visit once in a while but I think I'd tire of them as an example of "city living" pretty quickly if I were looking for that sort of thing.