I am almost in the same boat as you.... I have a D800 and a D3s Before I got my D3s I had a tough time deciding between the D800 and D4, I ended up buying the D800 and regretted it almost immediately. I ended up buying a D3s only 2 months later and now i use my D3s 90% of the time.
I am not a fan of the D800, the shutter sound itself drives me nuts. I will have no issue with swopping my D800 for another D3s or D4 if I could.