When pushing where the preview button is on the D300 on the D200, you get Menu instead of preview. If you push the Menu button on the D200, but you have the D300 in hand, you get the preview.
For many shooters this is not a problem, as the second body might only be used occasionally or as a back-up. For me, as a wildlife photographer (sports photographers will have the same challenges), I may switch between bodies every few shots. Why? Because I may be shooting a wide-angle or short telephoto on one body and a long tele on my tripod with the other body. When the action gets hot and heavy, I will be trying to cover all angles. No time to think which camera I have in my hand or which button is where. The last thing I want to do is miss the shot because a button is in the wrong place!
Well, that is exactly what happened in Costa Rica when I was at a Quetzal nest waiting for the male to return. I noticed something wasn't right. I inadvertently pushed the bracket button and, since I don't use bracketing, I couldn't figure out how to turn it off! Yep, the Quetzal returned to the nest while I was fussing with the buttons to turn off auto-bracketing! See the image above, all I got was the tail-feathers sticking out of the nest!
As soon as I returned from my shoot in Costa Rica I found a willing buyer for my D200. A good deal for him, and an opportunity or me to get a second D300!