Having had the honor of owning a ZL1 and now a C7 Z51, it's a toss up as to which car is better cuz it all depends on what you're into.
Both are amazing and very capable machines. Both go from 0-60 in 3.7 seconds. Both have a top speed of 185+ mph right off the showroom floor. Both have great handling with the magnetic ride.
It boils down to this...
Do you like a 4200 lb brick with 580 hp that gets 19 mpg and looks p***ed off just sitting still or a 3200 lb refined lazer with 460 hp that gets 30+ mpg and is elegant but deadly?
I LOVED both cars, but now only own a C7 Z51. IMO the C7 made my $61k ZL1 look and feel like a cheap, plastic toy.
Don't get me wrong, I still love Camaro's and as soon as I hit the lottery I'll have all kinds of them and Vettes in my stable.