Thanks to everyone for your input. You have pretty much confirmed my conclusion that the higher resolution of the D800 will not produce a print that is superior to a print made at the native resolution of a lower resolution camera such as the D200. As some have pointed out, other features of the camera (ISO rating, focus tracking, etc.) may allow one to take a better photograph; however, that is not the point of inquiry.
My understanding is that, despite the really good results one can produce by upsizing in Photoshop (ignoring other software that some say is even better), is it not true that a print made at the native resolution of a camera will be superior to a print made by upsizing? I therefore assume that, using the same comparison of a D200 and a D800, if one made a 16" x 20" print of an image taken with the D800 (requiring downsizing), it would be superior to a print of an image taken with the D200 (requiring upsizing). Implicit in my conclusion is an assumption that the downsizing of the D800 image does not diminish the quality of the print. Do you agree or have any comments?