5D2: Higher pixels (more details, you can print photos with larger size), better white balance ability (the automatic white balance of D700 is not very good, and the new firmware has some improvements, but it is still worse than 5D2), better viewfinder (the visual field of D700 viewfinder is not 100%, but it is quite bright), and video function.
Both are quite good things, so choosing these two machines mainly depends on which functions you pay attention to (see above), and secondly depends on whether you want to choose Nikon's optical system or Canon's system (see below).
Generally speaking, Nikon is more realistic, but more vivid and masculine than the real thing. There is not enough powder to shoot a beautiful woman (but it looks sunny, which has become the reason why many people say that Nikon is not as good as Canon, because sugar water tablets need that kind of powder feeling). The macro shot is beautiful, more stylish and absolutely cool. Nikon's big disadvantage is that the transition is not good, it is harder and slightly drier than Canon.
Canon is more freehand, delicate and soft, with natural transition and rich details. When shooting a beautiful woman, it is pink (in fact, the color is relatively red), and when shooting a man, it looks more creamy. As for the macro scenery, it's actually not bad, but the style is different from Nikon's, and the color of direct film is often not as bright as Nikon's.
Simply put, Nikon tastes heavier and Canon tastes lighter, depending on which style you prefer.
In addition, Nikon's flash technology is first-class. If you want to play flash in the future, Nikon will have an advantage.
Personally, d700 is more suitable!