Good question. If I owned a C5-Z06, I'd strongly consider it. I like the look of the C6-Z06 much better, and I like the "engineering enhancements" over the C5-Z06.
I won't lie and say that I haven't recently thought about selling my 1990 ZR-1 and using the money towards the purchase of a C6-Z06....but...I just can't do it.
As quirky as the ZR-1 is, it's in my blood. I bought her in 1994 with only 179 miles on it - plastic still on the seats and steering wheel. I've got about 29,000 miles on it now and I've had some of the most incredible times in that Vette. It's rare, kind of unique, has a bit of a legend built around it, and it looks and sounds cool. It's not only served as my personal play-thing, but also my psych-doctor. Anytime I'm totally stressed out and just need to unwind, the ZR was always there and after spending a good hour driving and having fun with it, I'd step out of it feeling completely regenerated.
To let my ZR go - even for a new, state-of-the-art, killer-Corvette...would be like me opening my door and letting my dog run off.
Even though I could have something much better and probably much more fun....I tend to hold a high degree of loyalty to some things and the ZR-1 just happens to be one of them.