Very important to try to keep a city 'clean' feeling. Sioux City is not clean feeling while Des Moines to me seemed amazingly clean, but I don't want to pay a state income tax just to have things more clean. (though it's not helping out Sioux City) There's a balance. I don't know the politics of the two cities but Sioux Falls is probably more business friendly and progressive.
Some people around Brookings say Sioux Falls and Watertown are both 'dirty' and it's true Brookings is a clean town but I still prefer Watertown and Sioux Falls more for their amenities... shopping, recreation, etc. Luckily it's easy enough to simply drive to either one. In any case I'd like to see Sioux Falls be a 'clean' fast growing city.