Until we see the camera, or at least the manual, we won't know for sure all of the differences. For example, does the D700 contain the built-in intervalometer function of the D3? Don't know. And there are other firmware features that are as yet unknown. Some may favor the D3; some may favor the D700.
The D3 AF is quicker than the D300 from the reports I've seen, but what, if anything, that portends for the D700 I don't know.
D3 has interchangeable focusing screens; D700 does not.