When we tested the Nikon 500mm and 600mm f/4 models the performance, while very good, was slightly behind that of the newer (and pricier) Canon models. In a slight reversal of fortunes, the Nikon 300mm and 400mm f/2.8 models actually appear to outperform the latest Canon offerings, at least when mounted on the Nikon D800 (though bear in mind this sensor has both high resolution and a wider dynamic range than the Canon EOS 5D Mk III used to perform the tests with the Canon lenses. Given the price advantage of the Nikkor lenses currently, Nikon users and potential purchasers can rest-assured that either model is a good choice and a sound investment in the long term.