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I personally like the silver color with the newer dark steel gray (Midnight Metallic Silver) which provides contrast. I can't stand seeing a dirty wheel and the gray wheels seems to look like it's covered in brake dust all the time. But gray wheel does look very cool on white or red cars.
Newscutter has the 21" turbine wheels. steph280 has the stock 19" wheels.
These are 19" cyclones on my Model S. (There's a subtle difference between turbines and cyclones which is easy to see once you know about it: on turbines, the vanes are evenly spaced around the wheel, while the cyclone vanes are arranged in 5 pairs, with slightly more space between each pair.)
Tesla posted a document claiming a slight range improvement with the cyclone wheels over the stock wheels, but it's a really inconsequential amount.