Originally posted by Yamanobori Well, all the examples I have seen, corner sharpness is great in the D800. You will easily print D800 files over 20x30. With the Nikon tilt/shift lenses, this will make a better choice for a Architectural photographer. As for landscape, it just comes down to subtle things like format and the sensor size difference.
There are reasons for choosing one camera over the other, but not for the reasons you have given.
I can tell you from 1st hand personal experience with shooting and testing various lenses on the D800, that not all is rosy with the D800 and edge/corner sharpness. It's very much lens dependent, especially with the exact same lens samples thats performed well in this regard on a D3s and D700. Secondly the current Nikon 24 PC-E lens when unshifted is especially sharp across the frame but quite a few samples suffer considerably away from the center of the frame when shifted...especially the more one shifts. All sorts of techniques can be used like focusing and then shifting, or focusing, shifting and refocusing (on various parts of the frame). The D800 is a most amazing and well performing camera but certain issues like edge sharpness do exist (like with the fabulous 14-24), which didn't exist on previous Nikon full frame bodies. Same thing can be said for the 645D and certain samples of lenses (even certain lenses period). Strenghs and weakness can be identified. Each camera in general also have their specific uses and strengths in certain areas...with of course overlap in a number of different applications.
Dave (D&A)