These are roughly in the same price class, though the Sigma is a little less expensive. In Canada, the Sigma is available for $949, and the Nikon for $1029.
The Sigma has a 10-year Canadian warranty, the Nikon a 5-year Canadian warranty.
Neither has OS or VR, but adding VR puts both lenses out of my price range (and I don't need the stabilization for shooting sports).
The Nikon seems to be regarded as a better built lens, with better optics (but some reviews claim the optical quality of the Sigma approaches that of the Nikon so as not to be as much of a factor in the decision making process).
The Sigma has the HSM AF motor, while the Nikon is AF, but not AF-S (the AF-S model is no longer available new, and is considerably more expensive even used).
Reviews of the Nikon indicate that the AF speed depends on how well the camera body can drive it (ie. faster on a pro body than on a consumer body).
I would be using a D90 and wonder if the Sigma with its HSM would be significantly faster in auto-focus speed than the Nikon? And, whether this should be an issue to consider given that the intended us of the lens is for sports?
Are there other issues I should be considering?
I would love to hear people's experience with either lens as well as any recommendations.