5D2: Higher pixels (with more details, you can print larger-sized photos), better white balance ability (the automatic white balance of D700 is not very good, but the new firmware has some improvements, but it is still worse than 5D2), better viewfinder (the view field of D700 viewfinder is not 100%, but it is quite bright), and video function.
Both of them are quite good things, so choosing these two machines mainly depends on which functions you pay attention to (see the content above), and secondly on whether you want to choose Nikon's optical system or Canon's system (see the content below).
Generally speaking, Nikon is more realistic, but it is more colorful and masculine than the real thing. It is not pink enough to shoot beautiful women (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 pink feeling). It is good to shoot landscapes at a macro, and it is more stylish and absolutely cold and cool. Nikon's big disadvantage is that the transition is not good, it is harder, and it is slightly drier than Canon.
Canon is more freehand, delicate and soft, with natural transition and rich details. It is pink and tender to shoot beautiful women (in fact, the color is relatively red and partial), but it looks more creamy when shooting men. As for the macro scenery, it is actually not bad, but the style is different from Nikon, and the color of direct film is often not as bright as Nikon.
Simply put, Nikon tastes heavier and Canon tastes lighter, depending on which style you prefer.
In addition, Nikon's flash technology is first-class, so Nikon will have an advantage if you want to play flash in the future.