I voted D4 for its speed, un-fillable buffer, AF quickness, and low light ability but it has me wishing for an 800mm to go with it. That's why I'm also waiting for a D400.
I also have been shooting my D800E and last weekend on BIF it came home with the better images, the detail is incredible assuming one can fill the frame greater than a DX camera. It's a real knock-down drag out battle between the D4/D800 cameras and my perceived leader keeps changing hands. Am trying out the new D4 firmware tomorrow.