That's funny. There are many owners here (including myself) that have had the best of both worlds, that is, the opportunity to own both a Z06 and a Viper.
I purchased my Z06 in April of 2001, I bought it when I was 22, so my experiences where probably not unlike your own. I modified my car quite extensively, exhaust, intake, suspension, HRE's, nitrous, over 462 rwhp, if your interested you can view it at
http://www.cardomain.com/memberpage/294811.
Granted I sold my Z06 months before I purchased my Viper, so I did not have the pleasure of driving one as compared to the other within a short amount of time, but I am certainly not as critical as you were of the Viper.
I did notice a few things, the braking system was not as responsive in the Viper, and the build quality was certainly better for the Z06. But I found purchasing the Viper was certainly a step forward, even with the Viper being 2 years the Z06's elder.
In response to your critiques here are my own:
1. The Corvette has the cheap plastic interior. In fact, this is well noted among most car enthusiasts and is a topic of extensive engineering for the C6. GM does not want to make this mistake again. I will note the Viper does not offer the most luxurious design, but it is very pleasing to the eye, and is significantly more ergonomic than the bells and whistles vette.
2. I am 6'-1" and I fit fine, but I can understand your argument at 6'-4". Comfort is not one of the things that would influence my purchase of a sports car. I tend to compromise that for performance and looks.
3. Again, I could care less how much I see or don't see over the hood of a sports car.
4. If you have the pleasure of owning and aftermarket shift kit in your Z06, maybe you have forgotten how rubbery feeling it used to be from the factory. This is one thing I commend the Viper for, it has a very responsive feeling shift as compared to the factory Z06.
5. Certainly, the sound is an issue, but it is very much an issue with the Z06 as well. I owned an f-body with the adjustable Borla prior to my Z06 with the B&B PRT system, and later the Borla Stingers . The f-body was hands down the best sounding of three. I would say the uniqueness of the Viper sound is a selling point over the Z06, and that only gets better with aftermarket exhaust.
6. I agree the Viper compared to the Z06, is not a ton faster when driving it by itself, but pit it next to the car in question, and it will seem a lot faster as the Z06 looses ground to it.
I would like to add one thing, and that is the looks factor. Increasingly Z06's are poppoing up routinely in my area, and the crowd driving them gets younger and younger. By comparison I rarely see another Viper, especially with an owner as young as myself. As a result, the looks I get when driving my Viper are unrivaled. My Z06 was quite a head turner with the 18/19 HRE's, and the custom nitrous system, but nothing compares to the Viper (even in factoy garb). As a young man in their early twenties, I'm sure even you can appreciate that...
Brian