The Vauxhall is running on the zeta platform, but it's also a sedan, with less Aerodynamics and more weight.
I'd expect to see the Camaro come around with slightly more power (in upper trim) and a lower weight... not to mention more aggressive gearing (possibly).
A sedan, no matter how sports inspired, is still a sedan. Coupes always tend to be slightly more aggressive, and that's how I like my cars
Edit: Which, in closing, means that the Camaro will not only outperform all of those cars for less, it will outperform them MORE, for less.