I'm one of the people who shoots both Nikon and Canon cameras,and I wish Canon would make a camera comparable to the D700. My 5D has image quality that's basically equal to that of the D3 and D700 up to ISO 1600, where the Nikons seem to pull ahead. it took Nikon almost 3 years to come up with a full-frame, 12-MP body that could compete with the original 5D on image quality.
As I see it, the 51-point AF system Nikon puts in its pro bodies AND its semi-pro/lightweight-pro capable D300 is an area where Nikon is ahead of Canon's 9-point + invisible AF point array the 5D and 5D Mark II are fitted with; personally, I find the 5D's AF system quite a bit behind what the Nikons can do, esp. when using off-center AF points. And the speed of the D700 in terms of shutter lag time, and mirror blackout time is pretty fast and responsive--the 5D feels quite slow by comparison. What the 5D and D700 share is the half-height body configuration, but the D700 has a pop-up and the 5D does not. Both have grip options, but the Nikon's grip + High Output battery Nikon combo elevates the D700 so equipped into the pro-level firing rate for fast action and faster AF response; the AF system only works when the mirror is down,and in viewing position--the faster the firing rate, the more times per second the AF system can collect data and send focus commands. With a camera that shoots at 8 fps, it's possible to get two usable frames on many sports action sequences; with a camera shooting at 3.9 fps, you get ONE CHANCE,only. The frame "before" and the frame "after" with a 3.9 FPS camera is usually totally out of consideration. Firing rate brings with it better,more-responsive autofocus capabilities,and also gives you a very slight cushion on peak action. Shooting at 8 fps is not for machine-gunning long sequences with the shutter release mashed down--it's a way to make the camera simply more-responsive when shooting critical sequences,where the lens is long, the DOF is shallow,and the action is happening fast. The difference between say the D2x's 5 fps and 8.2 fps is/was very,very significant. Basically,the 3.9 FPS of the 5D presents a problem for action work in that there's a full quarter second between frames,and the AF is very centrally-weighted,and no offense, but the 5D's AF system is simply not up to the task for sports photography uses. The 5D series is meant for people/wedding/landscape/general assignment work, while the D700 is designed as an affordable general assignment/sports/PJ machine where SPEED of operation (speed of focus,firing rate,shutter lag time,mirror blackout/latency) is a very high priority. "Horses for courses"as the British say.
As far as 1.28x on the 1D-series and the FF on the D700: the wider angle of the FF sensor makes indoor photography easier with many legacy lenses, like 24,50,85,105,135,180,200,300,and 400mm. For much sports/PJ use, the need is not for more reach, because you are already very close to the action. A crop-body camera makes your 300 TOO narrow-angle a lens for many events if you're shooting with credentials from a spot along the sidelines or court; a FF body widens out the angle of view,making your 300 and 400 much more-useful for many sports/PJ assignments. Now that sensors are exceedingly good, it's better to have a wider lens coverage,since cropping in post is now Sooooooo much easier than when we were shooting 2.7 and 4.2 MP bodies.
Canon really does not have a pro-capable half-height body priced under $3k; the 5D Mark II does not have the same specs or the same orientation as the D700. Canon *could* try to compete in the D700 space if it desired. Maybe they will soon? Who knows...