Our first Polar White (color code 149) C250 arrived today! To my eye the Polar White is a little brighter and a little more WHITE than the Arctic White. I would say that the Arctic White is a little creamier or has a little yellow in it. Of course, until I parked them right next to each other I would have said they were exactly the same color! I have included the side-by-side pictures for reference. Can you guess which one is which? 
The Polar White car is the luxury model in spot #34. The car in spot #35 is a 2012 C250 in Arctic White.