That is a hard call. How bad do you want a brand new car? The camaro will have never been driven, and all the miles will be put on by you. You ordered the car, so it will exactly the way you want it to be.
However, that is a good price for the vette, and 15,000 is not a lot of miles. I am assuming that you know how the car was driven/treated/maintained so that shouldnt be a concern.
They are both serious hardware and there is not a wrong choice to be made here.
The question that only you can answer is what do you think is the best fit for you?