I had this exact dilemma about a month ago.
My LBS carries both the C-dale, and the Giant.

I went with the TCR Alliance. It felt more lively, and more comfortable to me. When I cranked on the pedals, it just sprang to life much more than the CAAD9. I could tell that the CAAD9 was very efficient and was a very fast bike. But I don't think I lost any efficiency by going with the TCR, and I got a bunch more comfort and a 'feel' that I really love.
It's now a month and 300 miles later, and every time I get on the TCR, my decision is confirmed. It's just a great riding bike. I can mash up a hill and there is NO flex. Sprint out of the saddle...no flex.
But it's more comfortable over rough pavement.

If I had to do it all over again, I'd go for the TCR again.