I have both, but I might be selling the Vette today.
It has been a great car. Comfortable, good handling, reasonably fast.
But now it's just paying for mods/paint for the Viper.
Just a year ago I was thinking the same thing when I planned to sell my Mustang to get the Vette.
The Viper most closely approximates my dreams of a cool sports car. So I think that I'm going to keep this one for a while.
-Dean.