Nikon or Sigma 70-200 f2.8

Just trying to make an educated decision here. I am looking to buy a 70-200 zoom and have narrowed it down to the sigma apo hsm or the Nikon non VR non AFS version. I am also looking at the sigma 100-300 hsm.

My questions mainly deal with the AF speed. Is the Sigma HSM that much faster than the older technology Nikon. Also if you use the dedicated teleconverter will the HSM on the Sigma or the AF on the Nikon still work.

Any suggestions or good and bad experiences with these lenses, including the 100-300.
None of the camera shops here stock these lenses so I can not test drive them. I did buy a sigma 80-400 os but returned because the focus was to darn slow. I would like to have the nikon 70-200 AFS VR but it is just out of my price range.

Thanks in Advance for any info

AF speed depends on the body. I have that Nikon, and it's a little slow on the Fuji S2 (Nikon N80, basically). Very good on the F100 but noticably quicker yet on the F5. That lens is so sharp you can shave with it... ;)

I also have a Tokina 80-400 that's not a bad lens, but much slower than the Nikon. I've picked up the AFS and AFS-VR, and they're both a little quicker than mine. I bought the non-AFS before the VR was out, and the extra speed of the AFS didn't seem necessary to me.