My guess is the 50th car and the 03 Z06 will be quite different.
The Z06 will remain the hardcore driver's Corvette.
The 50th car will probably be more like a ZR1, ie: fully optioned, not quite the cutting-edge handling of the Z06 but with either the LS6 or maybe something a little more powerful. The 50th will probably be available as a Coupe or a Convertible but not as a hardtop.
If you're a gnarly terror of a driver, you're probably going to want the Z06.
If you like the idea of a very unique, collectable Corvette with lots of power but still a nice ride and plenty of convenience options, you're going to want the 50th car.
If you're a waxer with lots of money and need to have the latest, geatest and coolest thing in the hobby, you're going to want the 50th car.