Have test driven both 18" and 17". On smooth pavement, little difference (17" with narrower tires rides quieter). On rough pavement, 17's more tolerant. Could not really drive the car at track speeds, but the 17's give a nice, lighter (but still communicative) steering feel and handles nearly flat. I think it becomes a matter of taste; still not sure if I am going to get the 17" or 18" wheels. The 18's have a nice muscular look and fill the wheelwells better - but seem relatively common on both S and 2.7 models. In my view, the 17's have a appealing retro look which reminds me of a certain rear engine German 60's sports car. Apparently PAG likes the look as well - considering the visuals of the 2.7 (including the fold-out poster of the red model in the brochure) consistently show the 17" wheels.