Budget Telephoto Zooms

I'd like to get a lens for under $500 in the 70-300-ish range, used but good condition is fine.  I borrowed a friend's Nikon 70-300 AF-ED (not VR) and found it to be terribly soft and slow to focus.  I want to be able to shoot both portraits at a distance (so nice bokeh is a plus) and wildlife (so sharpness and focus accuracy is also important.)

Been looking at the Nikon 70-300 VR, the Tamron 70-300 VC (both on the high end of my price range) and the older Nikon 70-210 AF-D or the even older 70-210 AF f/4 constant.  Body is the D7000, my only lens atm is the 16-85 VR.

From the reviews I've read it sounds like the Tamron may be the best bet as it is supposedly the sharpest at 300mm and does everything else just as well as the other lenses, although the lower price of the older Nikon lenses is intriguing.

Is this the kind of thing where I shouldn't buy over the internet due to sample variation / personal preferences?

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