I believe it's a tough call and really depends on your shooting style and subject. That said, if your willing to lug the heft of the 200-400 vr it's a great lens.
If your interested in shooting some sports and some wildlife you may be able to get buy with a 80-400 vr. It has limitations, but it's light weight, and affordable.
The 500 is a awesome lens too. Keep in mind that you will need a sturdy tripod/head, and the means to lug the gear arround.
If you have the cash buy both the 500 and the 200-400!
It's really a tough call. I'd say if it were me I'd go with the 200-400 mostly for the vr, and afs as both lenses area relatively close in size and weight.
I dont think you would be dissapointed with the 200-400, it really is a great lens!