I would go with 15's for about 4lb or so savings per wheel if you don't want to drag down performance. (over 16's. . .17's are even more weeight) If you are shooting for looks only, then pick which you like the best.
(That is 4 lbs of UNSPRUNG ROTATING weight. At 55mph that is equal to....a lot of sprung weight. Not sure the conversion)
Depending on which rim you get, the look will vary. For example, I think a Polished lip and a colord center makes the wheel "appear" smaller than a solid color rim. But in reality, a 15 with 195/50-15's and a 16 with 205/45-16 tires are going to look pretty close IMHO. But the 15's will save you some $$$ with initial purchase, replacement tires, performance and fuel economy.
17's are just insanely heavy and costly. But its all about what YOU like.