What are your shooting needs? These 2 cameras have almost nothing in common besides being able to take pictures and have TOTALLY different audiences. I think your first job is to decide where you and your style fits in with photography before you can make an intelligent decision. I've done my homework... and the D700 is my choice for me.
I think a more realistic question would be D90 or D2x Considering a great condition used D2x is about the same price as a new D90. Comparing a D90 to D700 would be like Acura Integra or Acura NSX??
D2x can be had for dirt cheap nowadays, but I would take the D90 over the D2x. Though closer, at that point, I would want to take advantage of the newer technology. The D2x camera is a good camera, but its not a great camera (compared to what is out there today).
THat was kind of my thoughts too. I think the D2x is best served as a FF backup to a D3 or D700...maybe a cheaper backup for a FF wedding photog.
The D2x isn't full frame, it uses a " The high resolution is achieved by the use of a new Sony 12.4 megapixel DX Format CMOS image sensor" It's CMOS, but not full frame.
I'd like to shoot landscapes as well as weddings, fast action as well as low light stuff. I want my next camera to be one I don't have to replace any time soon. I love my D80 but would like to step up.