If I was going to buy a Cadillac (and all these concepts were available for purchase) I'd take a
Cien
If I remember correctly the Sixteen has all-wheel steering, which is a good thing considering it's dimensions. I think it's sort of ugly myself. I'll take a Ferarri or a Lambo for the money.
http://www.cadillac.com/cadillacjsp/...c16/specs.html
This says the wheels are 24" x 9"