The Nikon 200-400mm f/4 lens provides very fast AF with excellent sharpness, contrast, and bokeh. It has AF-S silent focus (similar to Canon USM). It has VR image stabilization (similar to Canon IS)
I own both Canon and Nikon DSLR's and use each one depending on my needs. I have the Canon 500mm/f4 L IS, Canon 400mm/f4 DO IS, & Canon 100-400mm L IS. How
do these compare with the Nikon 200-400mm/f4?
If lighting is dim, the f4 apertures of the Canon 400/f4, 500/f4, & Nikon 200-400/f4 will give you 2x faster shutter speeds than the 100-400L. In terms of sharpness, the Canon prime lenses are more resistant to blurring when using a teleconverter. If you don't use a teleconverter, then there is no noticeable difference in sharpness.
If your subjects quickly move closer/further (such as birds or soccer/football players) the Nikon 200-400/f4 and Canon 100-400L both fit the bill, with the advantage going to the Nikon 200-400/f4 for its wider aperture (which translates to double the shutter speed at the same ISO). This can spell the difference between shooting at ISO 800 vs ISO 1600.
If you plan to walk for several hours while carrying gear in your arms, the Canon 100-400L (3 lbs) and 400/f4 (4 lbs) are ideal since the other 2 lenses are 7 to 9 lbs. Even if you are a muscular guy, you can still get hurt - google 'herniated disc' and 'osteoarthritis'.
In summary, the Nikon 200-400mm/f4 AF-S VR is excellent all-around lens for sports and nature photography. It is a little too heavy for an all-day lens-in-your-arms hike, unless you store the lens in a backpack or rest it over your shoulder via a monopod. This lens definitely needs a monopod or tripod for support (which will also add weight).