"OK. So what I am hearing is that it all comes down to the issue of subject motion. I understand what you are all saying. I wish I could think of a way to set up a test of motion in low light and see the difference."
No, not unless you were comparing the two lenses for their hand holding ability or VR only and sharpness. If that was the case then maybe the new lens would be equal or win and that would certainly give newer technology the advantage. But there is more to image "quality" than sharpness. For some, all they equate to lens performance is sharpness. Read any Sigma post. But many of us are simply pointing out in the case of these two lenses that the 1 f stop can make a huge difference depending on what you are shooting and whether you do it professional or for fun(speed, bokeh, build quality, etc.) Whether it's very low light or moving subjects the image just isn't any good if it's blurry or marred by excessive noise, and that 1 stop and the next highest shutter speed can make a big difference. When I shoot dance events or plays, I would much rather have that extra stop and get a higher shutter speed than raise the ISO (or both). It's just horses for courses.