Upload & Sell: Off
May I ask why?
Sure! My take:
Continuity between bodies (simplicity, practicality) - no thinking about which camera you should use for which photo, which lens is better on this camera or that camera, etc, etc - just two awesome cameras that will perform exactly the same. ISO, file output, cards, controls, feel, etc.
Cost to performance benefit - The D3s is an awesome camera. You could easily get two for a total cost of..maybe $6,000. The D800 and D4 are also awesome cameras, of course, but not enough to warrant the price difference. The combo would be about $9,000, without bargain hunting.
I don't think you can go wrong with any of the cameras you're considering, truthfully. This'd just be my personal preference, for these reasons.