Could you post more about what kind of photographs you like to take? Where you see this hobby going for you? They are both great cameras. The D80 is geared more to the "developing" photographer, one who is still learning, and the D200 is more of a "pro" camera (as far as I know. Which is little. Make sure you talk to someone who knows their stuff.)
Basically, if you already have both, just use them! You'll figure out which one you like best. They're both excellent cameras.
P.S. I know what you mean about cereal at the store
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Nikon D50, Nikkor 18-55mm, Nikkor 50mm 1.8, Sigma 70-300mm APO DG Macro, Tokina 12-24
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