There are 4 versions of the Nikon 80-200. First was a push/pull zoom and focus. There was one ring, you turned it to focus,a nd pushed and/or pulled to zoom in and out. Second was the 2 touch. Came with two rings, one for zoom, the otehr for focus. Third was also 2 touch, but was Silent Wave. Third, is still 2 touch and Silent Wave, but also VR.
The sigma is close to the original two touch in focusing speed, but the afs beats it hands down. The Nikon is also better weather sealed, and just plain built better. Get one, and you will never have a problem with it. If you don't need the vr, just get the afs version.
The speed of the Sigma should be faster than the Nikon 80-200 in question, since based on the info. in the original post it appears the non-AFS version is being talked about. The AF-S version costs notably more than the Sigma. With the D70, the HSM in the Sigma will be helpful. With a faster body (i.e. D1 or D2 series) I imagine the speed of HSM wouldn't be as necessary, correct?