Canon 5D Mark ii or Nikon D700  

I'd go for the Canon but that's mainly because I already have Canon equipment. I think Nikon and Canon make equally good cameras, it's more a mather of taste.

The Canon is better, for many reasons:
5d has 21.0 million effective pixels, and the D700 only 12.1 million - If you upload photos at stock sites this is really important;
5d has starting ISO rating from 100 - and the d700 from 200;
5D is lighter only 850 grams and d700 is 1074 grams - thrust me the weight is very important if you carry with you the camera and two or three lens :)
Canon is more common mark;
and one more example 5D makes movie clips 1920 x1080 @ 30fps, up to 12 min and 640 x 480 @ 30fps up to 24 min, Nikon D700 does not. Well i think this is enought for now. If you have any other questions ask me and I will help you if i can.

Best regards