The CTS-V is a fantastic machine, but to achieve times like it does, you have to sacrifice ride quality. The STS-V will always be a better traveling machine, and it looks so much better than any other Cadillac (save the XLR).
As for trading in your XLR, that should be a even trade. My "Product Specialist", told me the car was going to MSRP at 60K, and probably cost me around 66K out the door. I am trading in a E350, so that should cut a good chunk out.
Unfortunately, the Product Specialist, told me that GM would not "allow" Cadillac, to put the 6.2 LFA V8 in the XLR. Something having to do with being better than a corvette. This is all from his mouth. Personally, I would love to see this engine in a XLR. The XLR is SUCH a better looking car than the Corvette, I think the XLR is more deserving, it just doesn't have the seniority.
It is the same reason why Porsche, will not make a Cayman Turbo/GT2. It would blow the doors off the flagship 911.