You are right the big lenses from Nikon gives a superior bokeh compared to the Sigma Sport, I own the Nikon 300mm f2.8 G VRII and the Nikon 200-400mm f4 G VRII which as you say are superior lenses.
cjc2 wrote:
I own the Sigma Sport version. It is a decent lens, but nowhere near as good, or as useful as a fast 400, 500 or 600. For the price, and for the weight savings, it is a great lens, but it's no replacement for the 'Big Guns".