Here is my take on it.
Like everyone else I have made a lot of assumtions. I assume the "hatch" at the front of the Corvette is a hardpoint that is the same size as the one on the front of the Anaconda. I have matched these to size. Once that was aligned the other elements on the two ships also matched in size. I have marked these on the images. I'm not sure if those parts should be the same size, but the result is that (taking the slight difference in perspective into account) the Corvette is aprrox. one third longer than the Anaconda, which matches rumors that have been around for a long while. This scaling also shows them as having almost identical width.
But then, who knows. All of this discussion reminds me of the 'arguments' that occured before Horizons was announced where so many people refused to believe it was going to be Planetary Landings...
http://i.imgur.com/MocqozT.jpg