My .02 cents? I owned a C5 Z06 for 7 years. I absolutely loved that car. I traded it in January and bought a 2009 C6 Z06. The C6 is tighter, roomier interior, gobs of power, and is just more refined all around. The Nissan is a different car, a nice car, but the two of them are different.
Best thing you can do for yourself? Drive both and see what you like. Cars are like people / we're all different -