You are better off asking that question here:
https://photography-on-the.net/forum/showthread.php?t=822524
Bunch of us switched from Canon. I did back in April 2010. (From a 1DMKIV + 5DMKII to a D3 + D700 and now D700 x 2)
Assuming the next logical choice for you in Canon would be the 5D2 since you own the 5DC, IMHO, the only advantage the 5D2 has would be the 21MP and Video. If you do not require those things then the D700 is the better camera, period.
The D700 does have the better AF system. Keep in mind the more accurate crosstype sensors are all bunched up in the center columns so compared to something like the 1DMKIII/1DMKIV, it's not as nicely spread out. But compare to the 5DC/5D2, it's still tons better.
Yes, 8fps with Grip provided you either use an EL-EN4 battery of AA's. The grip is very nice too BTW.
As for lenses, Nikon is playing catch up very quickly. They pretty have filled in all the blanks except maybe the 135L which is kind of a bummer. They are pricier than Canon counterparts and of course you can get "older" Canon lenses, for example 24L MKI vs. 24L MKII, 16-35 MKI vs. 16-35MKII for much cheaper and still have great USM focusing and IQ so that's something to seriously consider.
The Nikon 24-70 is better than Canon's, but it's more expensive. The 70-200VRII is a wash. 14-24 is a nice option as well and of course they recently came out with the 16-35 f4 VR. 105VR Macro is just as good as Canon's version. You've got the 24G, 35G (coming out soon), Sigma 50, 85G all covered too.
That said, if you are on a tight budget, I would think long and hard before switching. I say this over and over again. With Nikon, it's feast or famine. With Canon, you have much granular options. You don't sacrifice too IQ when you buy the "cheaper" f4 lenses or the non-L primes for instance.
Good luck!