Barry, Keep in mind that the D200's viewfinder only has 95% coverage so you aren't seeing everything to begin with. The D600's viewfinder has 100% coverage so it is the closest thing to "what you see is what you get". I wear contact lenses so I can see the entire image in the viewfinder, but occasionally wear eyeglasses when shooting. Though the corners of the viewfindee are cut off, it is not enough that it affects composition.
Back to your original question regarding viewfinder size, you will see more in the D600 viewfinder even with the cut off corners because it has 100% coverage.
Hope this helps...JL
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