Neither are exposing incorrectly if the meter makes the adjustment correctly. BUT, if those last test results are correct, I would think the d600 is the more desirable sensor. If I could get the same exposure with 2 stops less light or use a shutter speed 2 stops faster in low light... Man, that'd be nice. In effect, it makes every lens you own two stops faster in light gathering capability.
Dude, if you read the article they clearly state that the D600 is defective and is not properly stopping down the aperture.
So you're not magically going to get 2 stops more exposure with the same settings; what happened is that the camera (D600) doesn't physically close the aperture blades to the right stop, so that while you think you're shooting at f/8 it's actually shooting at f/5.6.
That's a bug, not a feature!!!