If you are not worried about the looks, 17s make good sense. Cheaper tyres, as you say, plus even wear, better ride, less shock loading on the suspension, better sidewall-damage resistance, a much better choice of all-terrain type tyres if that's what you want, and the spare tyre also then matches the four road tyres. If the roads you drive on are bumpy, pot-holed and/or gravel it makes even more sense.