There is no doubt that Canon D700 is one of the best in class product from Canon. I am using the US version of this camera T5i and I am fully satisfied with this. If you are new to SLR world and not sure how serious you will be with your passion for photography, this is the camera you should go for. The interface is much more user friendly than Nikon D5200.
Believe me there is really very little difference between shots taken by Canon D700 when compared with Nikon 5200. Under Lowlight condition, Nikon has slight advantage over Canon. However, till ISO of 6400 both the camera performs similarly.
The Nikon D5200 has 39 focus point(9 cross focus point) in comparison to 9(all cross focus points) but in Canon all the cross focus points are well spread out in comparison to Nikon which has all cross focus point at the center. Taking a shot of moving object is slightly better in Canon 700 in comparison to Nikon D5200.
Both Canon D700 and Nikon D5200 is great camera and each has their own merits and demerits and for sure you would repent whether you go with Canon or Nikon.