It really depends on what type of photography you do. If your photo shoot subjects are stationary, I would definitely go with a D800. You can even use it for the occasional moving car shot. If the majority of your photography is action oriented, then the D3 would be a better choice. I don't own a D800, but I've owned a D3 and currently a D3S. I shoot events, action sports and motorsports, so the D3S is perfect for me.
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